U-verse internet speeds not what is expected

Hello, I recently upgraded my service from the 18Mbps to the 45 Mbps. The technician came and swapped out the modems and got it working, however, I have run different speed tests on both my xbox and laptop, and show that download speeds are lower than 20Mbps. I was wanting to know if I could do anything to fix it. I am using both devices wirelessly because I would prefer to not have everything plugged in with cords running all my apartment. If it is not possible to get the 45Mbps at my apartment, I would prefer to not pay for it. I hope you can help.