Just got round to using my Oomph SIM for my daughters iPhone 8 and got the SIM not supported message. There's not way for getting past it so now she has a phone that's useless (unless I take the sim out again).
The reason you are getting this message on the iPhone is that the phone is locked to EE, you are going to need to contact EE for them to get it unlocked. Although VM use EE for their signal the SIMs are not EE hence the message.
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