Vodacom refusing to do an upgade that is due

I have 5 vodacom contracts, 3 of the contracts are due for an upgrade. I went to the vodacom shop to upgrade and was advised that because i made a cash payment on my account after the 3rd of the month I cant upgrade for 6 months. My vodacom account in an month is round about R 2500 - R 3000 which i always pay my account is not in arrears. I find it very annoying that i pay Vodacom so much money and they simply refuse to upgrade me. I will be getting Cell C to buy my contracts out from them as their service and attitude is extermly bad. I spent the most of my morning on the phone with the service centre either i get cut off or i get transffered to another person that cant assist. Finaly i got to speak to someone in the upgrades department which had an rude approach and kept interruptig me while im trying to explain why i calling while im explaining to her she is talking in xhosa to someone else. Vodacom will never get business from me again.