What was the agreement your company signed with Blink? Who owns and maintains the stations?
Answering those two questions should give you your answer.
Ideally you would be able to charge different rates depending on the card used, so employees can continue to get free charging, while everyone else pays. Or if your office is out of the way, keeping it free for all and just being able to plug-in and charge may be easier.
Does your company have plenty of charging stations for everyone?