Is it permissible for a shipping company to offer a customer a total price that includes the services of purchasing goods, shipping them, and clearing them, without detailing the costs of each operation separately, knowing that most customers request this, and that the company refuses to provide a detailed breakdown even if the customer asks for it?

We understand from the question that the transaction has two forms:

The first: The customer owns the goods and wants to ship them, and you inform him of a total shipping amount without details. This is permissible because the knowledge of the wage is achieved by it, and it is a condition for the validity of the ijarah (leasing/hiring contract).

The second: The customer does not own the goods, and he commissions you to purchase and ship them, and you inform him of a total price that includes the cost and the shipping fee. In this form, the shipping fee is unknown to the customer, and this is not permissible in ijarah, because one of the conditions for the validity of ijarah is the knowledge of the wage.