Is the work of a collections manager permissible, given that they are sometimes compelled to file reports against customers and detain them until payment, and is the work of a jailer permissible?

Your work in collecting legitimate debts for the company is permissible. You are allowed to pursue those who are late in payment if the company has authorized you to do so, and it is your duty to protect the company's assets. It is permissible to complain about debtors whose financial situation (solvency or insolvency) is unknown, unless you are certain that the debtor is insolvent, in which case you are not allowed to cause their imprisonment. The work of a jailer is originally permissible in imprisoning these and others. However, it is forbidden if he knows that he will imprison someone unjustly, because it is hiring for an unlawful act. If the ruler is oppressive and known for his injustice, then working as a jailer for him is forbidden, as helpers of oppressors are those who assist them in their injustice.