Overcharging customers :( Issue with currency charged not matching currency in cart

Hey! My website is set up and everything is working well, however, a customer sees a product advertised in GBP on page (£49), and then when they get to cart it says $79 NZD

That’s no problem, however they are actually being charged £79 which is substantially more than they should be.

This is the same with USD too.

After it occurred yesterday with GBP, I then turned “off” GBP as currency for payment, but it still happened again overnight. See screenshots which show the two transactions overnight. Those $$ amounts are incorrect, they are what should be charged in NZ or AUD.

The customer uses the converter on the product page, and then when they check out, it charges them way too much.

[Order #125595