monthly data costs are wrong

[Ruby771]

i called up on september 16th to upgrade my phone, when speaking to a team member they gave me a discount for my 5GB of data instead of it being £12 they offered me £9. however the discount hasn't came through and i am paying £12 can you sort this out for me otherwise i will cancel the phone and go with a different provider 

[caesarome]

@Ruby771 

When is your next billing date as the offer might be applied then or even the one after is that one is due to be paid soon so what do your future bills show ?