For a couple of years now I've been using my A71 with a UK SIM and a Thai SIM both installed. On topping up my Thai PAYG SIM the other day I noticed the SIM Manager was showing 'No SIM card' for the second slot.
If I restart my phone and then go to the SIM manager it shows the second SIM as active but, when I try to switch off my UK SIM card, it says I can't because I must always have one active. It then shows 'No SIM card' for the second slot.
I'm in the UK at the moment, and I know my Thai SIM card is still valid because I can see its validity, and top it up, through my online account with the Thai service provider.
If I swap the SIM card slots in the phone, the Thai card is operational but the UK one isn't. Any suggestions please, other than take it to my nearest Samsung service centre?
Checked again with the cards swapped, and it's even more confusing. With the Thai card in the first slot, and showing as active, I then sent a text message to my UK number. The outgoing and incoming message both showed up under my UK account.