Creditors calling wrong number?

We are constantly getting calls from creditors looking for my husbands ex wife. She has our phone number listed on past accounts and keeps listing it on all her new accounts. The collectors have her correct address but not her telephone number. Of course when the collectors call, they assume I am her lying to them. They don't stop calling no matter what we do. When we do manage to stop one, there is always a new one to take the last one's place. We've talked to her a few times about this, and she always says she doesn't know why they are calling us. It's obvious that she's using our number, even on her applications for new credit. Our biggest worry is how this may or could affect our credit. Any one have any ideas on what can be done besides sending the letter? We've done and continue to do all of that along with telling them not to call. Please Help!