Not happy with service

Hi I'm not happy with what Vodacom did to me I upgrade my phone last year November and I had a discount of 20gb on my previous handset which I asked if the 20gb will not fall of if I upgrade was told no and I received my new phone was happy with my new handset also received my 20 gb discount as well in November and also December but since last month I haven't been receiving no one send any communication regarding this now I'm only getting the small Dada which for the new handset and its less then 2 gb I'm now struggling because I was using this 20gb for my business pls assist