What is the ruling on working for a foreign telecommunications company that imposes late payment penalties on customers, and what is the ruling on selling lines for this company, knowing that one of the contract conditions is a late payment penalty on the customer if they delay payment beyond 21 days?

The fine imposed on a debtor who delays repayment is usury (riba), which is forbidden and void. It is not permissible to fulfill it. Therefore, it is not permissible to enter into a contract that includes this condition. However, if your work is limited to inquiries without directly engaging in, assisting with, writing, or witnessing that which is forbidden, then there is no blame upon you. Those in charge of the company are advised to avoid imposing such a forbidden fine.