This also happened to me. A few months ago, I was assured by Bangkok Bank and DTAC that my name matched, unsurprisingly as I've had the same SIM and bank account for 15+ years. But then, last week, got the message via BB that my online banking was to be suspended.
Went into DTAC and they said it was because I'd never updated DTAC with my new passport number (issued in 2018). So updated it, and Bangkok Bank updated their system.
I knew one had to tell the bank when we get a new passport, but it had never occurred to me to tell DTAC/True!