MY SPRINT PHONE BILL IS $580?

I have a Galaxy Note 5 32 GB. The plan is $20 for unlimited calls and texts and $23 for 24 months to pay off the phone. Then I had an incident in which I had to pay insurance $200 for a replacement phone. So so far it should be $253. Then I reviewed my bill online and I had a plan for my tablet too. Which is silly because the salesman never even said it had a plan. All he said was that it's a Black Friday deal and it's free. The tablet plan consisted of $15 for 1gb of data (Which I wasn't even told of) and $13 for insurance (which I also wasn't told of). So in total it should be aproximatly $281, wnich is still pretty expensive. So why is it now a total of $580? How do I fix this? If they refuse to fix it, could I cancel the plan (cause I'm not paying $580). And if I do cancel the plan, would I still need to pay the $580? What if I don't have enough money? (I'm on a budget) I know this is very long but it's very important so you need all these details.

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