Not so Instant Top Up

A few days ago, I top up my phone credit through Maybank2u. I chose the Instant Top Up so that I do no have to key in the top up number myself. This is my 2nd time topping up through Maybank2u. The 1st time it was INSTANT. Within a few second after I hit the purchase button, the received an sms informing that the top up amount has been come in. This 2nd time wasn't INSTANT at all. No sms and no airtime being top up within half an hour. I kept looking at my phone for sms notification but none till all 12 hours after I purchased it. I called the Hotlink Customer Service and was told that the top up has already been sent at 11.51 am. That is an hour after I purchased! When check, ya, it is in but why wasn't there any sms sent? Don't think I will buy my top up through INSTANT top up again.