ARREARS????

On 9th June I received an SMS from Mr price that my account had an amount of R300 overdue. My monthly instalment was R525.00 but suddenly I owed R825.00. I tried several times to contact the accounts dept on the number provided in the SMS but to no avail. I eventually emailed them and to date have had no response. My account has been up to date and the only instalment I had missed was end of May which I have since paid instore. I cannot understand the R300 overdue and am very disappointed with their service, or lack thereof. All I need is for somebody to contact me and explain what is going on. I have been a customer since the account system was introduced and have always made sure my account is up to date, even paying extra every month. The disregard they have for their customers is terribly sad