Overbooked flights

We have booked a flight 10 months before departing date.ona arrival at the o.r tambo airport ,the flights were overbooked and now we will arrive a day later.the lady assisting us was useless and unhelpful to pur situation. We have 1 day holiday and we have paid for accomodation that we lost out on. This is totally unacceptable and unprofessional.i will not be using kenya airways agains and i suggest no1 else does too