why do i not have heat in the front but it wrks in the rear? on 1998 Cadillac Catera

i reciently had the service engine light oil light and coolent lights reset on car after having it overhauled. new plugs wires oil change coolent flush by a sertified my temp read out is in celcius not farienheight no outside temp and blows freezing cold in the front but heat blows out hot in the rear? help please.

Asked by for the 1998 Cadillac Catera