Excessive Usage

<p>I received an sms notifying me of my virgin mobile debit order. It was approximately 3 times the amount of what I usually pay. I contacted the call centre and was told they didn't know why I was billed they will get back to me. On Monday I contacted the call centre again to find out my query was with accounts for refund or credit approval and I would receive feedback in 24 to 48 hours. I then contacted them again today and was told that my account was incorrectly credited ( with no way of me knowing )with airtime that I shouldn't of used hence my bill. How am I to know I have received airtime incorrectly? I have a top up contract to avoid these types of bills and when my airtime is finished I purchase more. Apparently one should always check your airtime balance before making calls?????? I was on hold waiting for an indication of how much airtime I was incorrectly given and I eventually put the phone down as I couldn't wait any longer. I'm still waiting for a return call! </p>