Hi ​@Rayne 

I do apologise that you have been having an issue with receiving OTPs. Please note that OTPs are only sent via text. If you are trying to get a replacement eSIM or access the app without a working eSIM or SIM, you will not be able to access as the OTP is only sent via SMS. Please contact live chat for further assistance Live Chat Support | iD Mobile Network

If you already have the replacement SIM activated, you will need to make sure that your mobile number is correct under settings. 

For android: Settings > About Phone or About Device > Status > My phone number.  Some Android phones will have SIM or SIM card status listed within Status.  This is how you will be able to find the number you are using on your phone and sim. if using Message App, Change the phone number associated with the Messages app:  Open the Messages app.  Tap More then Settings then Advanced Select Phone number then edit the number to the correct phone number associated with your SIM card.  Tap OK.    If still have issue, remove the SIM and reboot the device.  Then re-insert the SIM and check if its updated the correct port number in Phone settings.    Still have the same issue after rebooting then advise try the SIM once in different device and see while sending text does it shows temporary number or port number.

For iPhone: Please go to Settings> Phone> My Number. Please change it to the number you wish to keep. If it fails to save the number. Tap General. Scroll down to the bottom of the list. Tap Reset. The "Reset" option is at the bottom of the Settings menu. ... Tap Reset Network Settings. Enter your passcode if prompted, then tap Reset Network Settings to confirm your choice. This will help.

-Owethu