Boston businesses school very selfish

I register a booking course at 2015 and i ask one of the consultant to advise me with something that will accommodate my shift at work course my shift keep on changing .but one when i was attending my class i couldn't log in they told me that my contract has been expired i was so suprise and they told me that i know exact coz i was once study at Boston long time ago .and they told me i must pay all the money for that course as the contract says .th thing is they call me to pay coz im still owing the school yet i paid everything dispute of not successful having my certificate. And i have a proof of payment of R00.and they hand over me to their debt collects .