mortage company refuses your payment

We refinanced our mortgage in August 2008. Even tho we paid on line, we always received a monthly mortgage statement in the mail every month. We paid our mortgage on line 3 weeks early every month until June 2013. This is when the mortgage company locked us out of our account. I even went to one of their banks to make a payment only to be told, we are sorry but we can't accept your payment. They couldn't tell us why. I called them many times only to be told that is was in legal and they didn't know what the problem was. I asked them how can I pay my mortgage? Only to be told, we are sorry but we can't accept your payment. They even stopped sending us the monthly mortgage statements. I called a asked for a detailed payment schedule of all payments that we made. We would call them or they would call us once a month. Each time was a difference person and I would have to go over everything again and again. So fast forward to July of 2015. I also saved all papers that were sent to us during this time and I also wrote down the dates, times and person I talked too. We finally got a statement sent to us and it was asking for all payments that they refused and that we could just pick up where we left off paying our mortgage every month. They still couldn't tell us why we were locked out. Yet for 2 years we never got served a foreclosure and as I said they stopped sending us the monthly statements. They finally started foreclosure proceedings in October 2015. So we had to go and retain a lawyer just to try and get answers of why we were locked out and to find out what makes them think that they can foreclose on a customer for a problem that was caused by the montage company not me the customer. They told our lawyer well they were late. Nope they weren't. Oh wait, they missed payments. Yea, because your locked them out without explaining what happened. Our lawyer asked them why didn't y'all file for foreclosure back in 2013? Still couldn't get an answer to that question either. So the lender was going forward with the foreclosure and we accepted it and the show down was going to be in court. Well not sure what happened but our lawyer filed some paperwork addressing the problems they we had with the lender and that we still couldn't get any correct answers. Attached was all the proof that we made all payments 3 weeks early until for unknown reasons we get locked out. The mortgage company got served these papers and decided to not proceed with the foreclosure for some reason. The judge permanently stopped the foreclosure and refused to issue another court date at all. The lawyer we have is only for the foreclosure only. So my question is can we sue the mortgage company? They are the ones who locked us out and REFUSED to take any payments at all. They have yet to explain to us why this happened and expect us to just do as they say. What legal grounds do we have to hold the mortgage company liable? So for being long winded and thanks for any help.