Hello. ive just

Hello. ive just returned home from dentist. im in process of having root canal done on my lower right 7.(my right lower back tooth) dentist says they cannot find 1 of my root canals and can refer me to specialist. im on income support and cannot afford £600. other option is to have it extracted. is there anything I else I can do as it,s 1 of my chewing teeth. Sure I read somewhere about having a scan done on it. Has the xrays at dentist don’t show roots up.