As I posted below, same thing happened to my Maxroam sim. It just died. Don't know if they are related issues. I think Celtrek uses an Israel +972 number too like Maxroam. May be the same carrier. Maxroam is sending a new sim to me with my credit transferred over.
http://www.prepaidgsm.net/forum/maxr...-t2427p15.html
Phones: Xiaomi Mi Mix 2, Samsung Galaxy A50, ASUS zenfone 3,
Sim cards: AT&T (Contract), 3 UK, Piranha Mobile