Three UK have a complicated abuse checker implemented. For every calendar month, if you spend time roaming on a Feel At Home partner network you must also have your SIM register on the Three network in the UK at some point in that calendar month.
Failure to do that for 3 times in a rolling 12 months will automatically end your roaming privileges.
That implementation is designed to prevent someone buying a Three UK SIM and using it as a global traveling SIM. It's designed for people who instead travel between the UK and other destinations frequently. (i.e. their SIM will check in on the UK network at least once per calendar month)
Three UK have a complicated abuse checker implemented. For every calendar month, if you spend time roaming on a Feel At Home partner network you must also have your SIM register on the Three network in the UK at some point in that calendar month.
Failure to do that for 3 times in a rolling 12 months will automatically end your roaming privileges.
That implementation is designed to prevent someone buying a Three UK SIM and using it as a global traveling SIM. It's designed for people who instead travel between the UK and other destinations frequently. (i.e. their SIM will check in on the UK network at least once per calendar month)