Praise be to Allaah.
There are two aspects to this question.
Firstly: what can you do to solve this problem?
Secondly: when can you go for Hajj without the debts leading to your Hajj being rejected?
With regard to the first issue: try to pay off your debts to the people you know about. Whoever asks you to pay back the debt and has proof that you owe him, or you can remember that you owe him, pay him back. If you know that you owe somebody and how much you owe him, but you cannot find him, or you know the amount you owe but you do not know to whom it is owed, then give that amount in charity on that person's behalf. If he comes along later, give him the choice between approving of the charity and gaining the reward for it, or asking you to pay him back, in which case the reward (for giving charity) will be yours.
With regard to the second issue: if you want to go for Hajj, then you can either pay off your debts, especially those where you know how much is owed to whom, or you can ask for their permission and then go for Hajj. May Allaah help you and make it easy for you to pay off your debts and fulfil your duties.
Sheikh Muhammed Salih Al-Munajjid