Similar happened to my wife five or so years ago.
It started off receiving phone calls in middle of night but when answered there was no-one in the line. Then her phone stopped working. Phone Vodafone and told there was a technical problem with her phone or account by their foreign call centre a number of times. After four days they reinstate her account but don’t explain anything else.
After the weekend she went on a work trip and her card is declined. Account emptied of thousands of pounds.
Vodafone finally admitted wasn’t a technical problem but fraudster had cancelled her Vodafone account so she couldn’t get notifications from bank and setup online banking on her account (she didn’t do online banking then). Phone calls in middle of the night were obviously fraudster checking to see if phone had been turned off yet before they plundered the account.
I still blame Vodafone for not telling us what was happening with her account in the first place. It took ages to sort it out with them and get the early cancellation fee refunded. Unfortunately Vodafone at the time were the only service provider which worked in our area so we had to continue using them.