They r suppose to give u a reason what...Not sure about ur prob...r u somewhat have ever been blacklisted or problems with CCRIS/CTOS?

Nope....They may tell u if they want but not a must.

If you call CS general line they most probably won't or can't tell you the reason. However, if you apply thru a MBB staff, and you got his/her contact number, you can call him/her and they can check what is stated in the system.

If you go and sit down with an officer at their branch, they can tell you the reason. I also got rejected when I first applied for a Maybank CC. I was at their branch when I got the news so I straightaway asked. The reason was that they found out my savings acc with them contained too little $$. I forgot that I even had an account with them! 
So I told the officer that my salary goes into another bank, not MBB, hence the low amount of $$. He then amended something into their system and then asked me to wait for a call from them. True enough, two days after that, I got a call saying that my application was approved.

I also have a maybank saving account and just like you that account did not so active because I am using RHB as my default account. Better go to the branch tomorrow. Thanks for the info.