Best answer by Mohammed
The quickest way would be to try putting the SIM in a phone to see if you can get the text of the code and complete registration.
If that still doesn't work, we'd recommend getting in touch via our Social Media Team so we can provide the code to you.
The reason I suggest social media is because the code would expire over email due to the time-frames it takes for a response.
You can reach us on Facebook: https://www.facebook.com/idmobileuk/
We look forward to hearing from you if you're not able to resolve this yourself.