Has anyone else had problems with Dtac pre-paid sim cad billing/usage? My credit evaporated after I topped up January 12 on international calls Dtac say I made December 13. It is a pre-paid card. The online usage shows no calls or sms' made/received on Dec 13. On Jan 7, 9 and 12 unconnected/missed local calls with my Phuket land lady on her local/Thai mobile show up online as international calls and consumed all the credit. A top up made and confirmed by Happy sms January 12 had gone 36 hours later when I tried to use the phone yet in that period I'd made/received NO calls and/or sms. It is a basic pre-paid phone sim card, had it 15 months, no previous problems, not used for any data/internet, never used for that at all. I'm thinking of getting a new sim card with AIS and having to change my number since Dtac cannot resolve or address these issues. It's bizarre, anyone experienced this before? Is AIS worth switching to?

Turn off mobile data.

Most probably you have apps connecting to Internet, which in turn uses your credit.

All data is "off"; have never used this sim card for any data/internet, only telephone calls and sms, nothing else. Dtac say the credit was consumed by a non-existent international call on December 13, Dtacs site shows no calls/sms,nothing on December 13. And yet it's a pre-paid card, so how can Dec 13 usage be "unpaid" until I topped up January 12? The "international calls" listed by Dtac on the billing/usage are missed/unconnected calls to/from a local Thai mobile number.