Mobile phone contract

[MamanPapa]

I have taken in July a mobile phone contract for my son at £9.50 per month. I asked for it to be capped. the first 2 direct debit were ok. £9.50 but then I noticed that the last were at £14.50. I phoned the provider and they said to me that there is an extra allowance on my contract of £5.00, something I wasn't aware and I don't want. They don't even want to take it off.
Has anyone had a similar experience?

[BadToTheBone]

Question exactly what the allowance is, when it was added and if it forms part of your contract. My provider has a cap and only if you click to buy extra will it go over my allowance. Is it possible your ds is clicking to add content?