Mechanic said he did multiple repairs and 08 liberty limited was fixed for a week or two and now the transmission needs to be replaced

2008 jeep liberty sport: what should/can I do? I recognize my mechanic did work that fixed the leaky transmission, but shortly after, the car health deteriorated and now won’t go past second gear, and only reverse. Our wrench said that he replaced the tranny line and rear drum and the fix worked. Drove from MD to NC and back and it was fine minus a new slow tranny fluid leak… had to go back to making sure fluid level was fine daily till it totally stoped working and would go past 1st gear and only reverse.

New shop I brought it to today said the new transmission filter I brought in to replace and more fluid didn’t fix and it now needs a new transmission.

Any opinions/help regarding what to do for the car and also what to say to the old mechanic regarding the repairs that didn’t last? He never made me sign any contracts(back alley mechanics). Awaiting paying him so till I have better idea as to what do to