Shifting hard and revs up

When car is in low gear the rmp's go up and down. When I give it gas it acts like it does not want to go and revs up. I let off the gas and wait a few seconds and give it gas and same thing happens, it also will jerk. Some times it will go but crawl to get up to 25 mph. I have had the transmission serviced and I am still experiencing this problem. It also shifts hard. Help please. Thanks