@OvEr_KiLLAs soon as you change tariff it bills you so when you topped up £10 it will have taken the charge instantly.
If you want to check this with Customer Services then you will need to contact them on 4445
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iPhone 16 Pro Max - o2 and Spusu
Xperia 1V - Spusu
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This is not customer services and we dont have access to your account
I do not work for o2 or any VMo2 /Telefonica/Liberty Global Company