Once a Payment Gateway has been used, it cannot be deleted. The Gateway will need to be inactivated which will remove it from use and as a feasible option for use later. The Gateway will need a password entered to be able to inactivate it.
To inactivate the gateway:
- Go to Core > Settings > Payment Settings > Payment Processing
- Edit into the desired gateway and uncheck Active
- Make sure you have a password entered for the account
- Click Save