I did originally provide this information as a comment to RianFL's solid contribution, but felt that it warranted full solution status.
If you are serious about completing the full Rockstar Table Tennis retail, please note that if you trade wins with someone to get the 3, 4 and 5 match winning streak achievements you can jeopardise getting "The G.O.A.T." achievement.
I had six losses (from boosting this achievement) when I tried to get the GOAT and it took 155 wins from a level 50 player (Gamertag: Qwanimal) in order to reach level 50. Essentially, you will be heavily penalised for any losses. The weighting for the skill level in this game is very harsh indeed and if you ever played online for fun it may be practically impossible to ever earn the GOAT.
I know it's tempting to knock out the streak achievements for easy gamerpoints early on, but it can make your life very tedious if you wish to get the GOAT later.
You have been warned! ;o)