Why can't I get a booster with my iphone 5s?

For my birthday a few days ago my mum bought me a Iphone 5s… It's not on contract and it's from EE and I'm on T-Mobile.

Anyways I want to try and get one of those boosters where you pay £5 and get internet for a whole month as I can't use the internet when I go out anywhere so I can't speak to my friends on wattsapp.

But if I text MONTHWEB to 441 which is what you have to do to get it… They keep telling me to please try again… Why?

Why doesn't it get through and I topped up £5 today as well so I've got credit… They take the £5 out of my credit… Right?

sorry never had a smartphone before

Thats weird

Give T-Mobile a call and check. May be you should activate web on your number first.

Check here: https://www.t-mobile.co.uk/....co.uk/ee/