I interpreted the parent comment as how to react if the Mastercard network goes down worldwide when Russia retaliates by trying to hack them.

Payments networks inside Russia is another matter altogether, but I assume like most countries they also have a local card network (Edit: found it, it's called Mir[0]). In that case, the issue will arise only when trying to use russian cards outside Russia.

[0] https://en.m.wikipedia.org/wiki/Mir_(payment_system)