Absolutely ******* service minutes after taking out new contract

I took out a new contract on 11 Aug and was promised 10 gigs free data up front. The data was pro rata'd and hi only got 6.7gigs. I call and the after sales department tell me I have to go to the store. I had to double check if my insurance was moved to the new phone and it wasn't. Then they were supposed to debit my account on the 25th and they didn't. I call to ask what's happening and no one has an explanation. I am told to go to the store. What is the point of having an after sales department if they can't deal with telephonic queries? Why should I make extra effort of going to a branch to ensure payment happens to you!? And you're staff is rude. It's pathetic