No reply from collection agency now what?

I have been going back and forth with the agency and they replied to three of my letters with not enough information I have requested and now they have not replied to my last two mails. I sent it certified mail so there was a signature of someone receiving it. What do I do now? Should I get a lawyer and try to clear it from my credit report or should I write to the 3 credit bureau explaining the situation and ask them to remove from my credit report. If so is there a sample letter I can use?

Thanks a million