Depends on the problem and what is required and can they get access etc. Took EE 7 months around me. Most of them trying to get permission to fell a tree.
May not even be O2's mast
Use WiFi Calling at home if you can
https://www.o2.co.uk/connectivity/wifi-and-4g-calling
O2 does not guarantee 100% uptime in any location, no network does.
This is not O2 and we are all customers here similar to yourself and cannot answer account type queries.
