By default, if you have an "All Cards" surcharge on the backend, that same surcharge will also apply to online ordering.
If you want your bank surcharges to differ depending on whether an order was made online or at the POS, you will need to:
Set up surcharges for specific cards on your POS - note that this means that you will always need to select which card type was presented every time your customer pays by card
Set up surcharges for all cards for Online Ordering
Note that you will not be able to charge different cards different amounts for online ordering.
On the backend, go to Sales > Surcharge and tick By Card Types.
Create a surcharge for All Cards with the amount that you want to charge for online orders.
Create a surcharge for Mastercard with the amount that you want to charge for POS orders paid with Mastercard.
Repeat, now specifying the Visa surcharge details for orders made on POS.
You should now see 3 surcharges in the table. Repeat steps 3 and 4 for all the different card surcharges that you want to apply on the POS.
On the POS, go to Settings and enable A18. REQUIRE SELECTION OF CARD TYPE UPON CREDIT CARD TRANSACTION. This means that you will always need to select which card type is being presented at the POS. You will not be able to toggle off A18 as long as you have 'By Card Types' selected in the backend.
Sync payment info on the POS.
Now, when a card transaction is made at the POS, the surcharge for a specific card will apply; when customers place an online order, the All Cards surcharge will be automatically applied.