existing customer but wont let me change current sim price to new deal price of £7

[Lfcgod]

My son wants a new iphone 14, as existing customers we want a new sim deal of 15gb at £7 but changing sim plan wont allow me to get this deal just says £14 for the same thing. How do I get the £7 sim deal as an existing customer. thanks

[PandJ2020]

The deals are for additional SIMs.

If he has an existing SIM then use that.

If it's ok with a new phone number then purchase a new one and cancel the old one.

There is a convoluted way to port the number out of the network and back in again as an alternative.

(Unless you call Sky and they are prepared to apply the deal to a current SIM)