Hi Vince,
If phoning you should call at 8am to avoid call queues. I actually called around 4pm and the call was answered in 8 minutes. The guy on retentions was great to chat with, plus I received a discount of £30 on my current package.
You could try the text messaging service. Just send a text with a description of what you would like (regrade) to 07533 051809. Your message will go into a queue and a representative will respond to you as soon as possible. It may take a few days.
Unfortunately there are no offers on Premier Sports, but any discount on your normal price should offset that cost.