Can't have to open new paytm account, complete KYC there and port mobile number there, then link your mother number to current paytm.
this is the only way..
and now, they're not doing kYC for new accounts, so it Can't be done. Check once nearby paytm store whether KYC processing or not.
But new account doesn't need KYC because no wallet and UPI and other bills doesn't need KYC. So, just open new account, request in support to move mobile number and enjoy with your name (without KYC).