poor sound quality on receiving end of droid calls

I recently purchased two motorolla droids for myself and another person with our company. We have both been told by people on receiving ends of our calls that we sound garbled, unclear and hard to understand. This is happening with both phones. We have used the phones in numerous locations so it is not a service issue.We have tried removing the cover, holding phone closer and further from mouth etc. etc. I was told holding shift+alt+delete would do a soft restart and might correct it but I can not get this to work. Our customers are complaind so much that I am going to have to return the phones if we can not resolve the problem. Please help, I love the phone otherwise but all the extra functions are useless if no one can understand us.