The service fee covers what it costs to move money and deliver your top-up instantly: the payment gateway charge, the carrier or voucher supplier fee, and the systems that keep delivery running around the clock.
Where you can see it
The fee is shown as its own line in your cart before you pay, never buried in the product price. Tap the fee to see a short breakdown. The total you approve at PayHere is the total you are charged.
Does it change?
It varies with the order value and the product type. Smaller reloads carry a proportionally larger fee because the underlying gateway cost is close to fixed. Buying a single larger reload is usually cheaper than several small ones.