T-Mobile "scam" help needed

[Mister_K]

Evening guys,

Few days ago I have upgraded my mum from pay as you go to a monthly contract sim ("unlimited" data, X amount of texts and minutes) all for £15 a month. I have asked the guy multiple times whether the whole deal will be £15 and he has said yes. Today I have opened a letter stating the first bill which was £26 (inc VAT) and I was shocked.

So either the guy has made a mistake or actually attempted a scam (I doubt he would try and do that, why would he?)
My question is, what should I do? Is there anything the British Law can do to aid this situation?

 

[Taycat]

Usually there are 1 time installation/initialization fees that are applied.
Could you perhaps give a summary of what they charged you?

 

[St1ckM4n]

Ring them back with the agent name and the ID number of the transaction.

Be nice, explain your case, and you may get a credit for the difference.