Peace be upon you. It is not permissible to say 'O Ali, help me' if one intends to imply that the infallible has independent control over sustenance without Allah's command. However, if the intention is to invoke the Prophet Muhammad (peace be upon him) and his family (peace be upon them) in supplication, such as saying 'O Allah, by the right of Muhammad and Ali', then this is undoubtedly permissible. Followers of the Ahlulbayt (peace be upon them) intend this meaning rather than the former when they say 'O so-and-so, provide for me or grant me success'. It has been encouraged for sinners to go to the Prophet (peace be upon him) to seek forgiveness, as Allah says: 'And if, when they wronged themselves, they had come to you, O Muhammad, and asked forgiveness of Allah, and the Messenger had asked forgiveness for them, they would have found Allah Accepting of repentance and Merciful.' This does not imply that Allah needs intermediaries, but it is part of His wisdom in honoring His righteous servants. For more information, you can refer to this question on the doctrinal questions website: [Intercession by saying 'O Ali' or 'O Hussein'](
https://aqaed.net/faq/0184/). May you be successful in all good.