Channels scrambled

I lose channels constantly on my bedroom television.  We had a technician out who gave us "the only other box he had" which was a large big one.  By the time I got home that evening, channels were out again.  We changed the box with the one on our living room television.  Both boxes work fine.  My husband said the technician checked the service connection said the signal was strong.  We've replaced the coaxial cable ourselves but still many channels say temporarily off air or their unwatchable because the scrambled.  I'm an tired of this.  I'm paying a huge amount for cable but the service is terrible.  I've also just had cannels removed.  I chatted with customer service who stated I should never have been able to watch those channels and if I wanted them back, I had to pay.  This was an error made by cox but I have to pay for it and for the poor service.  I'm also told I'm on a contract for which I have to pay $250 for early termination.  Again, Cox Cable plans to make me pay for poor service, take channels away and want me to pay them a large amount to terminate a contract which they have not honored.  I need advice on how this will be handled immediately.