TRVs not working?

I had a new combi boiler fitted about a year ago but it was only used for hot water but I recently had central heating added to it but I have two problems first is that the radiators are hot at the top but cold at the bottom and the second is I cant regulate the heat in the radiators, if I have the TRVs turned down low there is no heat if I have them sort of in the middle there is only heat at the top, they will only give off heat if the TRVs are on full but then the radiators are very very hot so much so that my grandkids have bunt themselves I am looking for a solution