Question about collection agencies

I am having trouble with a collection agency that is extremely rude. They are unwilling to work with me to help me settle an old debt that is 5+ years old. They demand payment in full which is twice what the original credit limit was. This account has been passed from collection agency after collection agency and they have all tacked on fee’s to bring the balance up to twice the original credit limit. The company that currently has the account is called Apex Financial. There have been hundreds of people who have had problems with this company. I am extremely frustrated with them and to the point that I no longer will answer the phone when they call. The calls have finally stopped as I now have a new phone number. I know it is only a matter of time before they get my new number and start calling again. My question is is there any companies out there that are reputable that will work on my behalf to try to work out a settlement with them?

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First things first
have them validate the debt and fees legally
then lets go from there