In case anyone is actually following this at the granular level, the reasons I decided to pay the false charge were to both get instant cashless access of course but ALSO because of a faint hope that would solve the blockage of normal customer service (chat and call) on my app. It did not. I could have filed a double payment form before doing that with an explanation and just because I do now have an actual double payment doesn't necessarily mean Grab will agree with me. As far as they're concerned, I hadn't paid before. As stated before. it's not about a clearly unfair one time hit of 300 baht which is obviously no big deal, rather its about the entire application not being trustworthy for me anymore, and sadly that is still the case.