Have to go and fix someones bloody computer tomorrow

So basically,I have to go to where my mum and my sisters workplace is to help someone fix their computer for free. No pay whatsoever, it just p*sses me off so much to be honest, since I work like 35 hours a week, I have to go there after like 7 hours of work tomorow. I'm already annoyed just thinking about it because i think i don't have enough time to do my hobbies which is what I do everyday after work! I can't believe my parents don't understand my aspergers, a normal person fixing something after work, no problem, but with a aspie, doing these to disturb my normal routine is WAY more difficult for which is what they don't understand, also I don't see noone fixing MY computer for free when I have a problem with it, I had to PAY to get it fixed, of course my sister would try to fix it for them and she did't know how to, it's her workplace, it's nothing to do with me, it's difficult enough coping with stress levels at work having aspergers AND OCD, they just don't get it, my routine is not to do anymore work after work so I can calm myself down and relax all refreshed for the next day, not to CHANGE my routine

I hope you all understand what how feeling right now