Hey sajaha bashi ahru suggest me in this situations.......

I got a letter from collection dept. had a rental car wreck five months before.And the insurance was only basic, which resulted me to pay for that whole car. So i started paying in monthly basis, but that mf sent the claim to collection, and which is beyond my capacity to pay all at time. I am just worried here ki my credit gonna be zero, ok that is also fine. Do the collection dept. go to my bank account too, or to my credit cards ......... without my authorization and take money? What else they do? Please let me know asap. Thanking you all.