DATA BILLING AND BLOCKAGE OF THE SERVICE

My fiancee is having a contract for a Laptop with Altech Autopage Gateway from February 2015. On 26 February Its service sim card was blocked while it was still having more than 400MB data bundles. When my fiancee made an enquiry, she was informed that a sim card was used on making a phone which lasted not more than 5 minutes. I admit that on February a phone call which hardly last 5 minutes was made from this sim card and certain amount was charged for that phonecall. On March the same sim card was unlocked and an amount of 400MB data bundles plus 500MB were loaded and I assumed that 400MB was the one which was fortfeited on February. On March data bundles were depleted as a result a sim card was not used. On 17 April 500MB were loaded on the same sim card and we started to use it. On 8 May I noticed that the same sim card is blocked, and I personally phoned Altech Autopage Customer care Centre to make enquiries but I was informed that the same sim card owing an amount of R688,18 which was incurred between 19 March to 16 April.If that is the case why, the same sim card was not blocked on that time rather than blocking after a month because you are very good on terminating a servi