UPDATE 2-Kenya's Safaricom sees 20 pct customer growth

* Says market underdeveloped

* Says 2010 EBITDA margin similar to 2009

* To invest more in data services (Adds details, CEO quotes)

By Wendell Roelf

CAPE TOWN, Nov 12 (Reuters) - Safaricom (SCOM.NR), Kenya's biggest mobile operator, forecast 20 percent growth in customers next year in the East African country where mobile ownership remains low.

Speaking on the sidelines of an African telecoms conference, Chief Executive Michael Joseph Joseph also said the company expected its 2010 earnings before interest, taxes, depreciation and amortisation (EBITDA) margin to be similar to 2009.

Kenya has an estimated 18 million active SIM card users, which represents a 47 percent penetration rate in the population of 37 million.

"I see another 20 percent growth in terms of subscriber numbers because the market is under-penetrated and there is still room both in mobile and data," Joseph told Reuters.

Safaricom, which is part-owned by Britain's Vodafone (VOD.L), boosted its subscriber numbers to 14.5 million or about 77 percent market share in 2009.

The group's EBITDA márgin slipped to 40.6 percent from 43.5 percent on higher operating expenses in 2009.

He said the company would invest more in its data services and expand its money transfer services. Earlier this month it said revenue from money transfer had jumped in the first half. [ID:nSP535847]

"We only have the opportunity to expand within Kenya and we intend to expand that," Joseph said. ///

Safaricom said customers of the M-Pesa service -- used to transfer money to friends and families, as well as pay bills -- rose to 7.99 million from 4.14 million last year.

Joseph said the average amount of transactions a day was $10 million. (Reporting by Wendell Roelf, Editing by Tiisetso Motsoeneng and Erica Billingham)