Problems with Dtac Pre-Paid Billing

[FforestFach]

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?

[Forkinhades]

Turn off mobile data.

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

[FforestFach]

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.