I can relate to this issue, and understand it completely as I have experienced this myself. My account got deactivated without any notification whatsoever. I topped my account up with IDR 200, 000 and used to promo code to get IDR 100, 000 free. I only used my account once after that and I only spent about IDR 25, 000, after which, my account was deactivated. I called their customer service helpline several times for a month but I was either kept on hold for a very long time or they answered the call but never uttered a word (kept silent the whole time no matter what we said). I even visited their main office today and I got nothing in return. The staff came and vaguely said things none of which made sense. It was almost as though they just wanted to kick us out of there.
This is a very unprofessional behavior from them. I regret downloading the app and putting money in it. Gojek (another app like Grab in Indonesia) is much better. I have never had any kind of problem from them and I think that everyone using Grab in Indonesia should switch to gojek.