A few questions. Roaming turned on? PAYG or pay monthly? Apple or android? If PAYG do you have enough credit or pay monthly have you exceeded you spend cap or credit limit? Credit limit is only visible to customer services as all businesses set credit limits for customers. If you payment is due, or overdue, plus a low spend cap then you may have exceeded your credit limit. This should clear once payment has gone through. Raising spend cap may also help.
If you go into network settings try changing the network from automatic to manual and try to select different networks to see if this clears your problem
You can try live chat via the web but no idea how much success you will have getting through.
Final option try and get hold of a local SIM so you can keep in contact and email those important people with your temporary number.
