phone voice problems?

we have two identical iphones, purchased at the same time. We updated the software a few weeks ago on both...worked fine up till this morning...now making a voice call results in receiver's inability to hear voice clearly....all garbled. Both phones behave exactly the same. Took to an apple store, they said five similar complaints received and to wait for the software update....called at&t they confirmed it is not their problem, but other people are making similar complaints...suggestions?

<Edited by Host>