First of all you should have reported him for sending you a PM, that's if you have not requested him to do so.

Secondly, you why would you trust anyone online?

To all, if you want a credit card, go apply online or go to bank branch. If you apply at the malls, request for agent name card, if he can't produce any, then he may be just a part timer.

What's the username.... ?

What you can do now is to contact OCBC call centre and ask if there is any record of your application. Then maybe verify whether that guy is working for bank or just an agent.

ronnie meant well when he asked.
You should reveal the guy here for the benefit and safety of the members in the forum. Too many rouge agents these days roaming around because the cc market isn't what it used to be anymore.

What's so secret about revealing username ... this user may potentially "harm" others

Yes CS will say that and they are supposed to reply you in that format.
Questions
1. What card did you apply and what type ?
2. Did your income qualify ?
3. How much commitments do you have ?
4. How many card do you have ?
5. Any problems with your personal financial history ?

I don't want anyone reading your posting, thinking it is alright to appeal just because application did not go through. Sometimes there's a mismatch between the qualifications and the application, so card will not be approved - accept it. Credit card approval are tighter these days.