There is no email you can mail .
Today in this internet era, there is no faster service. Only customer care number and each task leads 15 days time to solve but practically nearly 1 month to solve.
I want to change my mobile number, but 15 days over no solution.
Any modifications( mobile, email-id, communication address, or surrender, ) it will take a long time and headache will be with you.
A card only offer is not a good one, it should be user-friendly in all aspects .
Worst, be careful please