My parent's told me not to attend this event but I'm going to go anyway.
Why would you do that after they told to not to?
Well actually, My Dad wants me to go but mum does not. I feel like my mum doesn't think I'm mature enough.
You should obey your parents. You shouldn't just be selfish like that and disregard your parents for that event.
You always seem to take their side.
Regardless of who's side I take it's still wrong to disobey your parents. In this case you need to talk to your dad and have him convince your mom to let you go. Just going anyway will upset your mom which will in turn upset your dad who may want to stop you from going to other things in the future, so he doesn't have to deal with the drama.