When credit cards are stolen/cloned, often the perpetrator tries to make some lowish value purchases to check if the card will work. I wonder if the sudden change to a new mobile network has triggered this?
At the end of the day, your credit card company are responsible for taking off any block, so hopefully they have done that to allow you to use the card.
From personal experience, the vigilance of credit card companies has been useful when we had a card cloned. They immediately spotted 'unusual spending' and blocked the card and contacted us. Although it can be very frustrating, it can also be very useful to have them watching out!
