Urs and Gm card

We have received calls from united recovery systems about a past due debt with our Gm card. We can still go online to our account and pay. I have caught it up current and scheduled payments online but the lady at Urs is demanding payment in full. We do not have payment in full and I am wondering what we can do. I have now been avoiding there calls because it just doesn't get me any ware. And the have even resorted to calling family members after we have spoke. I do not know what to do. Can anyone give me any advice. I don't want to be sued and I can't believe my ignorance let this happen.
Thanks,