Shopify is a global e-commerce platform, but it still has some limitations when it comes to local specifics.
For example, one of the most painful limitations for European merchants is the lack of multi-currency support for manual payment methods like Bank Transfer or Cash on Delivery, which are still highly popular in some countries.
The problem was that the manual payment was always in the store's default currency, calculated from the display currency. For example, if the customer saw the checkout total as 15 GBP, the bank transfer wasn't 15 GBP, but 453.23 CZK, as shown in the screenshot below.

The "standard" payment methods, like Credit Card or PayPal, work just fine.
How to enable multi-currency support
Shopify recently fixed the issue by enabling multi-currency support for manual payment methods. To enable it, just create the relevant market with a different currency, and your customers will be able to utilize the payment without any currency conversion.

That's great, but the only catch is that it's working only for Shopify Plus merchants.
Hiding manual payment methods per country
What can you do as a non-Plus merchant? Honestly, the best solution is to hide the manual payment methods on markets with different currencies. Otherwise, it will just create a mess for both you and your customers.

There are plenty of apps that can help you with that. We are using ETP Sort Hide Payment Methods, which is completely free and works fine.
Honestly, I am a bit disappointed that Shopify chose this "feature" to be the differentiator between Plus and non-Plus plans. There are many Shopify merchants in Europe who would benefit from this, as they are selling across multiple countries, and each may have a different currency.