Got dialing tone over my calls and when i press handset button?

I only deleted some numbers and added a few more on my BT Studio 1100 for first time. Then i added a pin number and now i get what sounds like a low dialing tone over all conversations and i can't hear callers. I have gone throught the book several times and it does not appear i have done anything incorrectly. I have never had this before. Help please.