Second hand Car

Last November 2015 I met a couple through online selling a 2nd hand car and my mom and I are looking for cheaper 2nd hand car so we decided to meet the couple to view the car and it happen in Bulacan where they reside and then January 13, 2016 we buy a vios model 2016 automatic transmission with conduction sticker YZ 1640 and it cost us 340K but we notice that the left side was damage due to minor accident and the color of it was fading so we tell to the seller about it and then they was willing to replace it but it tooks them month to be able to do that and they replace it with vios 2017 manual transmission with a conduction sticker VX 3757 on July 4, 2017 so i ask another replacement of the car because i was not able to drive the manual transmission so they ask us to gave them additional 70k to replace it with mazda 2 2016 automatic transmission conduction sticker RK 1273 of last july 25, 2017 we were able to travel to la union and while were on express way going back To manila the bottom car engine cover was tempered we go to mazda pasig to inquire about it after going to CASA a certain ms. pascual was messaging me informing that the mazda was a carnap and asking me to return to them or to HPG but i talk to the couple who sell the car but they told me it was not carnap because the documents are with me and also the main and duplicate key so we decided to just surrender it to the bank PSBANK in makati where it was loan by ms pascual after that we (me and couple) talk that they will return my money a total of 410k or they will give me a sedan any car just a collateral for money and they will give my money back until December 2017 they were not able to give it and they only gave me 50k last march. I am planning to file a case so that i can get ny money back because my family badly needed it. Can you please give me advice what will i do?