What can i do to make sure they get the message?????

i use to believe that the guys in my pe cl were nice and just imature...but now i know what they are... every time we go outside to play soccer i stand behind the net so when they kick the ball over i return it and get to watch them play... and i have allways done this because i am just that type who takes her own time and effort to do things for them... and i thought they appreciated it untill today... they began calling me giraffe and there are only 2 people who i allow call me that... and i didnt appreciate it... so now i am refusing to continue doing this for them because they arnt showing me any respect and i am mad... so i believe that they dont appreciate good things when they have it... so what can i do to make sure they get the message loud and clear????