What is the ruling on an employee at a telecommunications shop increasing the call charge for a customer, in order to take his right that the customer is procrastinating in paying?

Procrastinating on paying the full cost of a call after the service has been rendered is impermissible. This falls under the category of unjustly consuming people's wealth, unless the shop owner willingly foregoes it. The shop owner should set a price for calls that both parties agree upon, as sales are based on mutual consent and a known price. If the customer does not adhere to the agreement, he should not be allowed to make the call. If the shop owner is compelled to take his full right, there is no objection to that.