Can't send message with o2 - error 0

[SarahG24]

I desperately need to reply to an NHS message with a 4 digit number. It keeps coming up with an error (can't send message with o2 - error 0). I have checked my message settings on my phone and their are no premium restrictions and also tried on another messaging app. I've contacted support via an online chat and they have said that there are no restrictions on my account. My phone is a Samsung. Its driving me mad and its so important I try and reply. Please help 🙏 

[jonsie]

A zero spend cap will stop you replying even though the text is free

Guide: Spend caps on O2 

We’re just customers like you but it sounds like you’ll need someone to access your account which can’t be done from here. If you message O2 using the links below, they should be able to help you with this

or give them a call on 202  or 0344 809 0202

[SarahG24]

I've already contacted o2 and they said there are no caps/restrictions