Ok, mine can’t exceed £25 for some reason

Maybe your iD account has a lower credit limit @charlieivie? 

Suggest contacting iD customer service about your bill cap limit - get in-touch using their online chat service at https://idmobile.co.uk/live-chat, and type “talk to a person” once you’re connected.

Alternatively, get assistance from iD Mobile using facebook (Messenger), or Twitter (by DM), about upgrading.

The iD agents work between 9am - 8pm on weekdays, and 9am - 6pm at weekends.
Outside these times you’ll get an automated reply.

.

Maximum I can set mine to is £25 too. I have an excellent credit rating with all three credit reference agencies. 🤔

EDIT: I just found this:

1. Choose your Bill Cap - You can now choose an out-of-plan spend cap between £0 and £25 when you buy your plan. Or you can set a cap anywhere between £0 and your credit limit on your existing plan using the iD Mobile app or My Account online.

Same here!! I’m a home owner with silly amount’s available on credit cards. I guess it’s the nature a cheap network, more risk aversed.

I remember seeing my iD account had a credit limit of £100, though I’d set my bill cap to £5 when joining and never changed the setting.

Mine has always been set to zero, never tried to change it.

Adding into this, 

The maximum credit limit is £75.00.

You can either be set to £25.00, £50.00 or £75.00 and this is determined by your credit score at the time of purchase.

You wouldn’t be able to increase it past your credit limit. 

Mohammed