Also to update what happened. Managed to chat with a live agent who confirms the number is eligible for the free 6 months and renewal is automatic as per their system. Since it was not auto for the first 2 months, I tried to get more detail as to when the renewal will happen. Agent gave the date 29-Aug but not able to give the time, citing the time will be random / for different subscriber. So if line is not being renewed by 2359H then need to contact them again.
Then later in the afternoon, my Uncle said he got an sms about $10 top-up to the heya wallet. Not sure is it coincident or something had been done. Anyway will need to go thru it till the 7th month where we suppose to see the $5 top-up option.