Conflicting information

I received an SMS from Markham indicating the balance on my account and the installment amount and that is due by 01 August 2015. The SMS ended with a number that I must call. I called the number (about 10:30am) and was told by the person that my account was in arrears for about 4 months and that to avoid being handed over I have to make a payment amount as indicated in the SMS by the 01 August 2015. I told her it was impossible that my account was in arrears. I was told to contact customer care if I had further queries. Upon contacting customer care I was told that the contact details that they have for me is incorrect (even though I received an sms on the very number they claim not have, and that I receive my statement and mag via post at the address they dont have), after updating this info, I proceeded to query the arrears and was told in no uncertain terms that the account was up to date and that a regular payment was due by 01 Aug 2015. I am totally confused now, I have the receipt of payment last month with me, but dont want to risk being handed over to lawyers as a result of their mistake.