bill cap reached and now i cant use my phone

Hi, I am currently in Japan, I had to make a call to BA due to an issue with our hotel and they kept me on hold so long I hit my bill cap, since then my phone has not worked at all for calls or messages, which has made the trip a struggle so far, such as when I need a message for two factor authentications. I have data due to my Esim.

I can't extent my cap past £75 where it currently has reached, any ideas how I regain calls and text functionality? 

Thank you