Los Angeles-based SmarTalk Teleservices Inc. confirmed it has signed an agreement to purchase an Ohio firm for about $65 million in stock, the third major acquisition by the prepaid telephone calling card company in two months. SmarTalk plans to purchase privately held ConQuest Telecommunications Services Corp., a Dublin, Ohio-based developer of prepaid phone cards with about 200 employees. SmarTalk makes and distributes prepaid phone cards to such major retailers as Office Depot Inc., Ralphs supermarkets and Staples Inc. The deal would increase SmarTalk's distribution network by 6,000 stores to a total of more than 35,000 nationwide. It also would boost the number of SmarTalk's employees to 400. SmarTalk's shares rose $3.88 to close at $17.75 in Nasdaq trading.