UPDATE 1-Weak economy driving customers to Leap, Boost

NEW YORK Dec 9 (Reuters) - Leap Wireless International (LEAP.O) and Boost Mobile, a unit of Sprint Nextel (S.N), are both seeing increased interest in their services from customers looking to tighten their belts in the weak economy, executives from the prepaid service providers said on Tuesday.

Paying for calls in advance is seen as giving some consumers more flexibility as they can limit calls or budget for calls in advance rather than postpaid monthly bills, which charge for the same number of calling minutes every month.

"We're seeing an increased interest in prepaid in the past three months," said Boost president Matt Carter in an interview with Reuters.

He said the weakening economy is causing people who would have chosen postpaid contracts before to instead opt for prepaid services as they are "doing more due diligence" in looking for the best value.

But he noted that the economy also is causing prepaid customers to look more carefully at the number of calls they are making and whether they can avoid making them at the most expensive times of the day.

Boost plans to offer nationwide calling under an unlimited calling prepaid plan in the first quarter in an effort to expand its options, Carter added.

These services would compete with those of Leap Wireless, which specializes in selling unlimited calls for a set fee in its customers' local area on a prepaid basis.

Leap's Chief Financial Officer Walter Berger also said on Tuesday that it too is seeing strong customer growth as the economy worsens.

"In the third quarter we saw strength in October with respect to net customer additions. Thus far we're seeing such trends continue," Berger told analysts at a UBS investor conference, adding that the company had a good Black Friday, the day after Thanksgiving, a key shopping day.

"We're also seeing the benefit of flight to value" because of the economy, said Berger. While Leap customers are typically people with household incomes of below $50,000, Berger said it is now seeing more interest from people in higher income brackets.

Sprint shares were trading down 5 cents, or 1.8 percent, at $2.68 in early afternoon trading on New York Stock Exchange. Leap shares were up 2.1 percent at $28.01. (Reporting by Sinead Carew; Editing by Brian Moss)