Medical advice refused by employer

Hi Atty. I have question po. I work in a BPO company for over a year. Before ako magfile ng Leave of absence (no pay po ito) para sa surgery ko, i was transferred to a dayshift and different LOB position then retained (or I thought I was retained). Then after surgery, my Surgeon adiced me to rest for recovery for atleast 7wks which I cannot afford po. Pumayag sya na mag work ako nung sinabi ko na call center at dayshift naman ang work ko. He made a certification advicing to work in a dayshift until fully recovered. Pinakita ko po ang med cert dahil natransffer na pala ako back to graveyard while on LOA,nalaman ko lang nung tinawagan ko ang Tl ko. Sabi nila na they cant do anything even if I have certification from my Surgeon dahil naforeard na daw ang list sa clients. I just want to go back to work. Their basis daw ng pag transfer nila back to graveyard ay metrics ng agent, I have great metrics naman same as sa mga naretain sa dayshift. Is it legal for an employer to deny request with medical reason? Thank you po in advance!