Allied

My fiance has been paying $100 a month to Allied through wage garnishment for one year. I guess the contract was set up for one year and he forgot about it and now 2 months afterwards he realized the payments were not coming out and Allied called him demanding the remaining balance of $5000 in full or they will sue him. He stated to them that he was willing to make payments but they declined and kept demanding the amount in full. When my fiance asked for their address, they asked him why and kept giving him the run around but finally did give him the address. My question is if he sends them payments on his own, can they still sue him? Or how should we proceed from here?