Bad credit, fired from walmart?

When i was 17 i stole some **** from walmart around 600 bucks, so they fired me and told me to pay them 1400 buck im like screw that so they said they will tell equifax or something. Now im 18 and when i tried getting a phone plan, they wouldnt let me. can anyone tell me what happened, do i have a bad credit score, is thier anyway i can fix this? is their any point in paying equifax 1400 bucks or should i wait 7 years for it to go away. im in uni. so i dont want this to affect me getting jobs. is their any excuse i can use to my employer for this?? (please no lectures on how im a thief, i know i am, im really sry bout it)