How soon can I end my lease with Sprint?

I was a Verizon subscriber for years and loved the service that was provided. Then I grew tired of paying a high monthly bill with not enough data so I switched to Sprint back in October (worst mistake). There I traded in my perfectly working iPhone 6 for a 6s and they paid off my bill and effectively ended my term with Verizon. The iPhone is a iPhone it's great but the service is so bad I could cry! I never have a signal and the LTE is unuseable as I never have any! And to make matters worse I'm paying more monthly for my service after I argued with the people on the phone saying my set price is 175 a month for my family plan not 256! They won't change it and I'm so done.

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