Cant send message to short digit numbers - e.g. NHS number 80870

[JonP]

I'm having issues with my Samsung S21 on a pay monthly contract

The NHS sent me a survey from 80870, asking me to rate their service, when I try to send them a score I get "Can't send message on with 02- error 0"

The same thing happens when I try to report phishing texts as spam.

Some people have suggested going to Messaging -> Settings -> Advanced -> and changing the SMSC number, however this is greyed out as +44802000332. I cant change it.  Some people have suggested entering an code of  *#*#4636#*#* on the dial pad, but this does not work for me.

[JonP]

I've previously attempted reboots of the phone, I'm in a good signal area.

Text messages to my friends work fine.

[MI5 · Accepted solution]

@JonP 

Samsung phones have a setting in the message app to block sending to premium rate numbers.

Your phone will consider any short code as premium rate, even if they are free to send, so check the settings first.

Also a guide here Guide: Text Message Tips (not sent or received) 

Similarly, a spend cap may prevent sending too.

Guide: Spend Caps & Charge to Mobile on O2 

If you message O2 on Facebook (https://o2uk.co/O2CFB) , Twitter (https://o2uk.co/O2CTW) or Instagram (https://o2uk.co/O2CIG) , they should be able to help you with this.

[JonP]

OK, got this figured out - needed to ask O2 to raise my spend cap from £0 to £5.  Was able to request this on the O2 app.

Even though short code replies to the NHS are free, they are considered chargeable according to O2, so the spend cap needed to be raised.