Vumatel/Supersonic Refund query

I am very disappointed in vumatel/supersonic on the 24th of June we paid more than we were supposed to by mistake, we have been calling ever since we sent proof of the payment but we still haven't received the refund, when you call the agents don't even know what is happening you must explain the same thing over and over again only to be told that they we will call you back and they never do, I am actually disgusted with the poor service we have been receiving