Globeshop is a service provided by Citibank exclusively to their credit cardholders. The is another one called Globaleshop and only American Express cardholders can use their service in Malaysia.

vPost as far as i am concerned, only provide their service to HSBC and UOB Bank credit cardholders in Malaysia. Not too sure which one is cheaper but your VSHub does look very expensive eh 
They will send you a letter.
Well, usually when someone from the bank call me regarding my credit card account, they will not ask for my credit card number or billing address etc. They will only ask me if i'm Mr. XXX. So it is a normal procedure that they do not ask for your debit card details. Even here in Malaysia certain banks will also call using secured line. Meaning it will appear in our mobile phone as private number.
Good to know 

When you personally call in their credit card centre to enquire something about your credit card, they will ask for your card number, IC, mother's name, billing address etc. This is normal.