new for old problem

hi guys, first time poster, and total novice. i bought a flourecent tube to replace the old light bulb fitting in my garrage. there are two light switches at either end of the garrage. when i took the old light of, there were 2 sets of wires spliced together . the red was connected, the earth was connected together , but the black wires were seperate and at either end of the round bulb mounting. so i put my tube up connected the two earths together the two red together and the two black together bulb comes on fine but both light switches dont work, what am i doing wrong apart from trying to save some money on an electrician. thanks very much for your help and nice to join your forum, joseph.