When will the £5 a month, 2.25gb deal show for current customers?

You’re currently offering 2.25GB, unlimited texts and 250 minutes for £5. I’m currently paying £5 for 1GB of data. I’ve attempted to change my deal in the following ways:

• Your app, which doesn’t show the deal.
• The live chat, who just refer me to the sales/upgrade team.
• The sales/upgrade team, who say that they can’t see the deal on their systems.

Therefore, as a current customer, how do I get this deal?