The sub-currency is added as the base currency after payment

[kamal amer]

The base currency in my site is the dollar USD

One of the payment options with Visa is through the Egyptian pound (EGP).

When the customer, for example, buys a domain at a price of 6$ and in Egyptian it is equivalent to 180 EGP

The payment is completed successfully
$180 is added to the client’s account and $6 is subtracted from it, leaving $174 in the account balance

This is not acceptable because the amount is supposed to be 180 pounds and no credit is added to the user

Because the converter converts from pounds to dollars and calculates that the price to be paid is 180 Egyptian pounds, and upon successful payment, it must show that the customer paid only $6 and does not put $180

 

[xboy]

This is a very big problem IN whmcs!

[Saroha]

This is not a WHMCS issue. this issue is related to the payment gateway module. Because the module marks the invoice paid with the amount. 
The module just sent the number, not the currency type that why it happened. you need to contact your payment gateway to resolve this issue with their module.

or you can change some code in the callback process and response file because in these files the gateway returns the currency type but they do not convert it into your base currency. 
you can do it by checking and changing their codes. but we suggest you just raise a ticket to the payment gateway for it if you manually install the module and if the module is provided by the WHMCS then open a ticket on WHMCS.