Credit limit dropped without warning

In July, I upgraded my daughter's contract at MTN Greenstone. Immediately afterwards all 5 lines were suspended. I returned to the outlet, and the consultant phoned somebody who unblocked the lines. <br> <br> Every month since then, on the 9th, all the lines are blocked, and I have to phone 808 to get the lines re-opened. I have been told that is because the credit limit has been exceeded, or I have not paid. Payment is effected by debit order on the last day of every month, and has never been refused in over twenty years that I have had the main line.<br> <br> I have been given the number *** to call the credit vetting department, and have been holding over 15 minutes now, which is not acceptable.<br> <br> Please can you find out why the credit limit has been reduced to such a low level that each month's account causes the lines to be blocked.<br>