When you start to register in ChatGPT,
When you put your mobile number they refused to send me a code with the following error:
It looks like this is a premium phone number. Please provide a valid, non-premium phone number to continue.
To solve it 
Just add your wife or girlfriend mobile number 
and 100% it will work .
I’m just joking, but the way is you have to add another mobile number which is not linked in your mobile. Use any other mobile near you like your wife’s ,friend or if you have a second mobile. 100% you will receive OTP.
All the best