iPhone XR. Wont receive specific text

Hi,

Ive got a new XR and it’s taking me ages to sort out the texts, first off EE hadn’t allowed me to receive short SMS such as two step verification, that finally got resolved. My latest issue is that I need to text this number once work to get a unique WIFI login. I text it loads of times but don’t get no reply. People in work text it and they get an instant response with a generated code. Can any one assist. It’s driving me crazy.