Do mechanics have to honor there own warranty? Can they take as much time as they want on warranty work?

In Feb. of this year, I had my transmission and air conditioning worked on At a cost of @ $2500.00 They rebuilt my transmission and put in a new condenser for my air conditioning.They asked for a cash deposit of $700, I paid it, they finished all the repairs in less than four days, I paid the balance in full,in cash. was told I had a 12 month/12,000 mile warranty on all repairs ,including the transmission. Approximately 2 weeks ago all the transmission oil leaked out, so I had it towed at my own expense and It has been untouched at there shop since then.I have been told 12 different stories as to why my truck is not repaired yet. Is there anything I can do to motivate them ?