Unacceptable from Cell C

I was contacted telephonically by Cell C in last week and I also received a sms from them that I must come in as I am eligible for an upgrade on one of my contracts. It expires end Sep 2015. I went in Friday afternoon (17 July 2015) only to be told by the salesman in store after being there for 45 minutes that I can't upgrade as there is ***** on my account! He contacted head office but their response was that I must call back on Monday as the ***** department only works weekdays until 17pm. Why did they contact me in the first place to come in and waist my time and petrol? Why did they not contact me earlier and inform me of any ***** on my account, as I am not aware of any ***** on my account? This is unacceptable behaviour from Cell C! Will Cell C give me R10 000 to buy myself out of their own contract? I am not happy with Cell C and will gladly wait till end Sep 2015 and get a NEW CONTRACT from VODACOM!