Vodafone is constantly sending me "sorry you don't have enough credit to send a text message" even thought I haven't been texting, and I have texts on my plan anyway. I've been told to try turn off iMessage and FaceTime which I have done and am still getting the messages throughout the day. It's become a real pain and now I'm scared to put any real credit on incase it's trying to charge me to texts I'm not even sending? I've ended up blocking the Vodafone number though that is not ideal. If someone could help me please
If you have an iPhone it might be trying to activate Facetime (sending an invisible international sms to the UK)
There are some circumstances as well when an android or iphone will attempt to convert group SMS into a PXT instead. This 'feature' can be disabled in phone settings - should be easy to google how based on what device you're using.