What should i do about my cell phone bill?

Because you are not sure of the charges, you need to dispute with the phone company. They will check their system and provide you an itemized statement. Someone in your absence might have used your phone for making the calls. If you can trace that person, you can ask him to pay the bill for you. The phone company knows that you are the subscriber. For them, you are responsible for the bill.

The law office also needs to give you the details of the debt and confirm their collections, then make your payments.

Did you ever dispute the charges with the phone company? As a former billing representative working at the phone company, there is no way your account would be turned over to an outside collection agency with a dispute pending. Sounds to me like you either did nothing with the phone company or their invetigation showed the charges were valid. I know that once your account is gone to CA, you have deal with the CA. I think you should send a dispute letter to the CA. This is why it is so important to deal with things as they come and not ignore them hoping they will go away. Good luck.