Is the aforementioned format for a software and communication networks maintenance contract, in which a lump sum is paid for the service whether work is requested or not, permissible or is it flawed by unlawfulness due to the prior unspecified number of working hours?

It appears that the transaction in question is a special type of ijara (leasing/hiring), where the questioner is considered a specialized employee who is given latitude by his employer if the contract duration is fixed, with permission not to attend except when requested, and a condition to complete repairs within two days of notification. This transaction has details: it is permissible to hire him for a specified period with a known wage and to grant him latitude. However, the problem lies in the condition to complete repairs within two days, as it combines a time limit with a specific task. This involves jahalah (uncertainty) and gharar (risk), for ijara must be estimated either by duration or by work, and it is not permissible to combine them due to the uncertainty this causes in the contract. This is the view of some scholars, except in specific cases such as extending the duration beyond the work. We advise that the contract should be based either on the duration or on the work, without combining them.