iPhone getting no 3G abroad one one network but can’t connect to another network to change provider

My iPhone (Uk) is connected to IWIND in Italy - but there is no working 3G. I have reset network settings, turned off 4g, restarted, reset, left phone off for hours, checkef for updates, checked carrier settings, turned mobile data off for all apps bar essential but no 3G. Try to connect to other network provider (ITIM works perfectly for my friend) and it says no service. Rang provider (3 Uk) and fully investigated with no answer. Here for work so having a nightmare getting anything done as need to be on the move (thus tethering my friends phone)

any suggestions welcome - fed up!