A change in your mobile plan deactivates your previous account and opens a new account on same mobile number. So if you login using same mobile number, you will land in a new account. If you had verified email id on original account then you can continue to login to that account using your verified email id and OTP. If not, you will need to contact customer care on email@example.com.
However, if you are using JioCloud via Google/Facebook login, you can continue to do so without any interruption.