A perfect catch 22, Japanese-style

My sim-card to my phone doesn’t function here and I couldn't feel more disconnected from the outside world.
I have just spent a good walk trying to buy a prepaid-card.
Which should be simple.
And it is, except their prepaid-card is not a normal sim-card, just a card. And it’s all written in Japanese. Hence we’re in Japan; fair enough, but I’ve implicit that you’re supposed to call a number and activate it.
But consequently my sim-card doesn’t work here - I can’t call the number.