on 19-01-2020 22:24
Untill your calling allowances and credit runs out.
OnePlus 6 (O2 & Sfr), Z3 Tablet (Three UK), iPhone 8+ (EE)
on 19-01-2020 22:26
If you have unlimited calls then you won't get charged.
However, some customers have been reporting that calls get cut off every 15 mins 30 secs I believe is the time. Never been cut off myself though on calls to banks and utilities lasting up to an hour at times.