! LaTeX Error: Option clash for package babel.

documentclass[article,11pt]{Latex/Classes/PhDthesisPSnPDF}
raggedbottom
setcitestyle{square}
usepackage[normalem]{ulem}
usepackage[greek,english]{babel}
usepackage{amsmath}
usepackage{amstext}
usepackage{wrapfig}
usepackage{graphicx}
usepackage{algorithm}
usepackage{algorithmic}
makeatletter
defNAT@def@citea{def@citea{NAT@separator}}
makeatother

documentclass[greek,<...>]{<class>}