No service

The last month my phone has had either NO SERVICE or I can see a phone provider service and 3G or 4G Listed but no connectivity/no data.

my phone only works on line or calls via wifi.

phone is and iPhone8 and I’m in Europe.

I have lived with this problem so long hoping it was an update that effected others and would be rectified.

any ideas?

if I buy a new phone and put my sim in it - will I have wasted money with the same issue?

If I test my sim in another phone will there be any detrimental effect to my sim?

what about if I test my phone with a friends sim?

how do I discover if it is a phone issue or a sim issue?

thanks

sallyanne