Tourists - Use official taxis & rides instead.
Grab has rarely met expectations for me. Drivers ask me to meet them at entirely different locations than the pick up points, scheduling a ride prevents me from taking rides in the current moment - causing me to cancel and pay extra fees despite having no desire to cancel, cars have arrived without AC in 40+ degrees C. People here have often advised me to use grab to check pricing the negotiate with drivers. After several negative experiences and failed attempts to acheive some degree of customer support, I highly advise using grab to understand good pricing but going direct to other channels instead.