Account suspended due to breach of agreement

We made an arrangement with Vodacom to only pay R2000 of our outstanding account and they agreed that without suspending our lines, we can pay the balance of the amount due at the end of March. We made the payment on 7 March 2015 but today our lines have been suspended. Upon phoning customer care, they informed me that our lines have been suspended due to a breach of agreement. Supposedly, we agreed to pay them before the 9th, which we did (we paid them on the 7th) but they only received payment on the 9th. Now they have suspended our lines because according to them we breached the agreement. This is not the first time we have had problems with Vodacom. I think this is totally unacceptable!