Guy Krief

Chief Executive Officer

Guy is Upstream’s Chief Executive Officer. He drives Upstream’s strategic vision and growth into new geographies and products. Guy joined Upstream in 2004 and since then has served in multiple Product and Innovation roles. Prior to becoming CEO, Guy held the position of Upstream’s Chief Innovation Officer.
Guy has also co-founded Persado, a Bain Capital Ventures backed company, where he has served as the company’s SVP of Product & Innovation, in charge of product management, algorithmic research, and software development.
Guy has followed a diverse career path, which has seen him own a French pastry shop, found a messaging start-up, write and star in his own TV comedy series and host his own radio show. He was also previously a marketing manager for Wanadoo, France Telecom, in Paris, which became Orange. Guy holds a Master’s degree in Social Psychology from the Sorbonne in Paris.

Andreas Petropoulos

Chief Operating Officer

Andreas joined Upstream back in 2007, in Account Management, and he now leads the company’s largest in population department, as Chief Operating Officer. He established the project management function at Upstream and has helped develop a number of functions, as well as operational and commercial roles ever since. Andreas is now responsible for leading the daily operations of the company, across a number of functions and continents. He is an Engineer by education, a holder of a Bachelor’s degree in Engineering from the University of Sussex and a holder of two Master’s Degrees; a Master’s of Science in Satellite and Mobile communications and an MBA from the Alba Graduate Business School.

Kostas Kastanis

Head of New Initiatives

Kostas joined Upstream in 2015, initially as Head of Strategy, managing the strategic and corporate development agenda of Upstream as well as its Corporate Communications function. He currently leads the New Initiatives Business Unit, aiming at researching, designing and implementing innovative solutions to be productised by Upstream.
Prior to joining Upstream, Kostas spent 8 years with McKinsey & Company, advising banking, telecom, industry and technology companies in Europe, Africa and Asia on financial, operational and organisational topics. He spent another 3 years with MasterCard, leading business development for Mobile Wallets in South-Eastern Europe.
Kostas is a graduate of the Athens University of Economics and Business in Operations Research, a Master’s of Science degree holder in Decision Sciences from the same university and an MBA holder from INSEAD.

Dimitris Maniatis

Head of SecureD

Dimitris Maniatis joined Upstream in 2017, as Head of SecureD. He leads the division that designs and implements Upstream’s carrier-grade platform, SecureD, which combines machine learning algorithms with payment processing workflows to protect mobile operators and their subscribers against online transaction fraud.
Prior to joining Upstream, Dimitris assumed the role of Head of Reprise Media, a part of IPG Mediabrands, a leading marketing communication, media and technology group. His role at Reprise Media followed the acquisition of the digital marketing agency he created in 2014, All Things Web, by IPG Mediabrands. Since 2009, Dimitris had built a digital team specialising in performance marketing, serving multiple projects and campaigns for companies across online travel, finance, insurance, cosmetics and consumer electronics.
Dimitris has been named Agency Titan by Google, for the CEE region. He has a passion for data and technology; and the insights that these can provide into delivering successful solutions in the digital marketing space.
He holds a degree in Software Engineering, from the University of Manchester, in the UK.

Natalia Mila

Chief Technology Officer

Natalia joined Upstream in 2008 as a senior software engineer. She has worked in several roles within the company, as a team leader and later on as chief architect and head of engineering, leading the design and implementation of Upstream’s mobile commerce platform. She is now the company CTO, responsible for its technical product, engineering and infrastructure functions.
She has more than 17 years of work experience in enterprise software, in companies such as Intracom and Intralot S.A. She holds a Bachelor’s degree in Computer Science from the National and Kapodistrian University of Athens, and a Master’s degree in Distributed and Multimedia Information Systems, from Heriot-Watt University, Edinburgh.

Nir Aloni

Chief Commercial Officer

Nir is Chief Commercial Officer at Upstream. He is responsible for the company’s sales and business development, across the globe. He has been with Upstream since 2008. Nir is an e-commerce and telecoms professional, with extensive experience in the management of companies, at various stages of development.
Prior to Upstream, Nir was the CEO at Smartrade, an international e-commerce company, selling and covering a range of consumer products. Before this, Nir was director of business development at ECI telecom where he provided strategic direction and managed key corporate opportunities. Previously, Nir was a team leader at Trigger-Foresight where he formulated business strategies, helping clients succeed, across a wide range of markets and industries. Nir started his career as a software engineer at Tdsoft ltd., a global provider of carrier-class telecom solutions.
Nir holds a B.A. in Economics and an MBA from INSEAD in Fontainebleau, France.

Panos Martinis

Chief Financial Officer

Panos is Chief Financial Officer at Upstream. Panos oversees the company’s finance and legal department and is responsible for financial planning and the coordination of investor relations for the business. Before joining Upstream, Panos was Business Planning and Intelligence Manager at Dell where he played a key role in the company’s penetration in the corporate market. Panos also worked in Washington D.C. as a Consultant at LECG Inc. and as an Associate at Deloitte & Touche L.L.P.
He holds a Bachelor’s degree in Finance and Public Policy Management from The Wharton School, University of Pennsylvania and a Master’s degree in Finance and Economics, from The London School of Economics.