yes its possible your carrier has roaming agreements in place with other carriers and your phone was doing its job by providing you cellular service.
so far i dont see anything wrong. you can go into your phone settings and restrict roaming on other carriers (at least on us htc one's).
if you are not clear on your roaming policy with other carriers, contact 3 and ask.
Signal & Coverage - Support - Three
so far i dont see anything wrong. you can go into your phone settings and restrict roaming on other carriers (at least on us htc one's).
if you are not clear on your roaming policy with other carriers, contact 3 and ask.

Signal & Coverage - Support - Three
