I also ported out 2 lines from Celcom last year July
1st line ported out few days before billing date, being charged full month bill
2nd line ported out few days after billing date, also charged full month bill
I’m aware the full month bill charge for porting out, so I didn’t call Celcom for refund on my 2nd line.

Out of my surprise, Celcom mailed me cheque for credit refund for my 2nd line in Dec.