Non payment of goods delivered

Mapkol Supply Services manufactured sports clothing for the school in March last year. The school kept on returning the clothes saying the people were complaining about the sizes. We tailored the clothes according to the sizes people indicated. For a year there was this back and forward of the clothing until we eventually delivered everything they wanted. it is now 3 months now that they have been promising to pay but in vain. the attitude and noncooperation shown to me is nothing but a disgrace, They do not care about the fact that the goods were funded and rental, tools, and labor already paid for the goods, This is a school that doesn't care and am wondering how they treat the children there.