Your Honest SIM should automatically have the right data settings. But sometimes you need to set them up. It only takes a second. Here are the instructions to set up your data settings on an iPhone:
Open the Settings App on your iPhone
Click on Mobile Data
Click on Mobile Data Network
Make sure the top line called APN says gamma
The MMS section should say:
APN: three.co.uk
Username: *blank*
Password: *blank*
MMS Proxy: mms.three.co.uk:8799
MMS Max Message Size: 307200
MMS UA Prof URL: *blank*
If you've set it up right it will look like this:
