Hi
If you send an email, it will take a day or two for them to reply.
Instead use their live chat option. I rescheduled my exam using the live chat option. It takes a few minutes for them to connect u with a representative but be patient. (took 12 min for me)
State the reason and ask them to transfer your appointment to Pearson Centre, Dickenson Road, Bangalore.
Do this ASAP before the slots get filled there. Last time I saw, there were slots before Jan 15th.
So please do it quickly!
Also regarding the paid mocks. I think there is no link between the paid mocks not working and your GMAT centre problem.
AjiteshArun might know better about this.
Do update the progress here!
Good luck! :D