Update
Kudos to all who suggested that I need to press cancel button after swipe. This process worked for me. Thank you all very much!
First thing I tried today after going to WM was to load my GB Card at Kisok. This was successful. This gave me some hopes that WM can STILL process OV as debit cards.
Then, I went to MO. There was a different cashier this time. I asked for a MO for $1999.02 (with 0.49*2 as fees). She said $2K please.
I tried to swipe my first card, and hit cancel. This time the screen was asking "$2000 need to be paid". But this was not successful, tried again and hit cancel. Then I got the screen where we SELECT ATM DEBIT.
Then, for my last $500 I was not able to get the above screen at all. I was bit scared as $1500 has already been approved and I was not sure, if the cashier can void my transaction at this moment.
After 4 successful failures, Finally I got the screem and MO. Yay Me!!
I just did a small talk with the cashier, asking if they have updated their systems recently. She said, probably yesterday night they might have upgraded some software on systems. This may have triggered this hit cancel thing. I have NEVER EVER PRESSED Cancel even once in my MS life till now and OV used to work like charm.
Sorry, If I panicked anyone here. My MS life was going smooth till now and all of a sudden this happened and I have no money to pay, so got scared a bit. In life all things will not go as we expect and we need to take this. Anyhow lessons learned. Thanks all again for suggestions.