unable to send texts to one particular shortcode number

[CMG]

I have been attempting to send a text to a competition line on 83070 which repeatedly fails to send. I have sent to this number previously without issue and have no issues with other numbers. 

I also tried it with a tesco mobile and a friend has tried on GiffGaff which both use the O2 network and those fail to send also.

as these have been tried from 3 different phones from 3 different sims the only thing i can think is that O2 have blacklisted that shortcode number.

Has anyone else come across this issue?

[gmarkj]

It might be worth checking if you have a spend cap on your account (assuming you are a pay monthly customer) to see if you have reached your limit.
You can see it as a bolt on in your my o2 @CMG.

[CMG]

they are all payg with plenty of credit. The texts cost 50pence plus usual text cost

[CMG]

also please note that I stated that this failed to send from THREE different phone accounts on three different phones (all different manufacturers)

[MI5]

@CMG 

You need to contact O2 to ask them.
All numbers are in this guide Guide: Coronavirus Community Help and Support 
When you call, you will be asked for the reason you are calling.
Stay silent for 15 seconds and you will be taken to the keypad options.
Press 2 for Everything Else
Press 5 for More Options
Press 7 for Anything Else which will put you though to someone.
You can also try saying "Upgrade" or "Fraud" to be connected to an advisor.
8.00am is the best time to call if you can.