iphone 4 volume control is spazzing

The phone was purchased in September of 2010, I know it's super old but I can't afford a new phone. I don't even have phone service. I live off of wifi pretty much. But that's not the problem, my problem is up until this morning my phone worked perfectly fine no problems ever. Now this morning I wake up and the volume control icon is on my screen and so I think maybe I must have just pressed it myself but when I realize that after five minutes it is still on my screen I knew there was an issue also if I plugged my headphones in the volume would turn all the way up on it's own and stay loud then decrease all the way to mute mode. Whenever I tried to turn the volume up or down nothing would happen. I've reset it, I've erased basically everything and I am still experiencing the issue.

I would bring it into the Genius Bar but I have to buy insurance in order to get their help and if I can't even afford a phone service plan how can I buy insurance for my own phone? I watched videos that said you could clean the charging port out with a toothpick but I didn't want to risk doing more damage to the phone. I can't use my phone because the volume control icon covers up a lot of the keys on the keyboard and blocks most of the stuff on my screen.

I probably won't be able to fix this but I really can't afford a new phone anytime soon, so does anyone know any methods they tried that worked for them?