Some Amish use credit cards.
Amish are definitely not credit-averse (after all that’s how most of them pay for their homes and farms), but credit cards themselves would depend a lot on local custom and Ordnung.
I’ve been in communities where they are surprisingly common, and in others where they are unheard of.
How do the Amish buy things, for that matter?
Some people are surprised to hear that almost every Amish adult will have a checking account, or hold one jointly with a spouse. If you do get a check from an Amish person, it’s pretty much as good as cash.
Out of around eight or nine hundred checks I’ve received from Amish folks, only one ever lacked funds–and that was only temporary due to a money-transfer glitch.
Many outsiders would consider the Amish way of making purchasing decisions traditional at best and sexist at worst.
Amish women will do general shopping and handle buying home items of their own accord, but almost always defer more substantial purchases to their husband–or at least prefer to make the decision in consultation with him.
Rare exceptions may include those women who run their own business, have a husband that works away a lot, or simply those particularly ‘liberated’ Amish wives, to use a modern term that doesn’t quite fit the context.
But many husbands defer to wives. I’ve often heard the equivalent of the quite modern ‘honey, whatever you think’ from an indifferent father.
Many mainstream Amish see marriage as a partnership, just as we ‘regular people’ do. And a lot of things mom just knows how to handle best, after all.