@Katie267Im afraid there is no way of telling, as anyone can withhold there number, it isnt even presented to o2 as the code at the beginning of the number dialled masks this.
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iPhone 16 Pro Max - o2 and Spusu
Galaxy Z Fold 6 - Mozillion
iPad Pro 11 M4 - Three
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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