What is the ruling on working with the same company that closed my account due to fraud, in the following two cases: either I work through another person's account who has not previously subscribed to the company, or I contract with small advertising companies that deal with it, and not directly with it?

There is no harm in utilizing the account for free to contract with small businesses regarding permissible matters. Paying a percentage of the profit to the account owner is not obligatory if the agreement with them was to use the account for free.

Advertisements are of two types: permissible if they are for permissible things and do not include any Sharia violation, and forbidden if they are for forbidden things like alcohol, usury, and gambling, or if they include a Sharia violation; based on the Almighty’s saying: "And cooperate not in sin and aggression" (Al-Ma'idah: 2).