hr mistake asked me not to report to work

Hi Atty! im a nurse. i applied as clinic assistant manager in one of high regard hospital in ortgas. after a series of exams and interview the hr asked me to report and informed me that i made it. so i completed all the requirements and had my orientation with the hr and endorsed me to the satelite clinic i will be assign. so i started as AM even without signing a contract and discussing my salary since as per hr, after 1 week of training is the contract signing. after 10 days of working i havent sign anything yet i keep on ffup-ing it with them, (anyways i have copy of it on my phone.) but on my 11th day of working with the clinic i received a call from hr asking me to drop by. so i went today, 13th day, and learned from them that there is a mistake. they had overlooked the endorsement and im not supposed for the position and asked me not to report for work the next day. they'll pay me nMan daw pero not as Assistant Manager rate but as Nurse rate (w/c is much lower) since eto daw recommendation ng VP. is there any legal case na pwede i file against them... kasi i feel so upset.. i spend too much for the requirements palang and im comfortable na may work ako and all of a sudden sasabihin nila d na aq papasok the following day because of their mistake. and may i add the damages they had done to me.. i have other offer but i choose this work over them and my self esteem its under my feet now... pls help me. will very much appreciate it. thanks.

seriously needs help...