Tanishq — Login problem in tanishq app

I purchased digital gold from tanishq app five months ago.That time login was allowed through email id but now the only way to login is through registered mobile no and OTP.This requirement bothers me a lot since my registered mob no is no more with me network service provider has transferred that no to someone else hence it is impossible to get OTP.we have complained to tanishq exceutives in this regard multiple times but they are not providing me a resolution.I am feeling cheated right now. I will file an FIR against tanishq pvt.ltd.