Wife got served papers, need advice

Hello, my wife is scared and I am too a little, but panicking won’t help. In 2021 my wife took out a $2500 loan to help with buying a home with her mom and brother. She has been making payments since and the most unfortunate thing is the last payment is supposed to be next week. She checked her account and 3 payments were a bit late and 2 were deferred, but loan is still supposed to be paid off next week. Well i’m new to this but I think in the papers it says that the loan was sold in 2023. But yet payments have continued since then and we haven’t seen anyone contact her about acquiring her collection. Now the papers say no payments have been maid and she has to pay $4k. Now my questions are is it legal for a company to sell the loan, but keep receiving payments? And also how do we navigate this situation?

EDIT: Thank you all for your suggestions and advice. First of all I talked with my wife and she told me she did take a loan of 4k but not one of 2.5k so we have to do some digging and figure that part out. As for the papers, we called the court and they said nothing has been filed yet, so I don’t know if the papers she got were just to scare her into paying or something. Then we called Upstart who issued the loan and all they said was they sold the loan to the other company and we needed to contact them. So my wife called them and they said to forward proof of the payments to verify it is that loan or a different one. I will update once again when we have a response from them.