Vodacom advertised upgrade deal but refuse upgrade

Ive been a Vodacom customer for well over 14 years and wanted to upgrade to a Sony m4 aqua as they advertise it for R229. I was told that i could do that but only if i pay an amount of R2200 and then a further R110 per month. I asked why i cant get the offer as advertised and was told that they dont know. After wich i went to another branch where i was told it was because i have been paying my account via cash payment instead of debit order. Even though i dont miss payments and have given them my debit order details countless times. Im fed up with Vodacom wasting my time and money. You are losing a very loyal client.