No, they're not scammers. The stoppage is part of the contract. Every legitimate cloud mining service will have such a clause because legitimate cloud mining services have to pay for electricity to power the hardware they actually have. Therefore, when the cost of that electricity becomes greater than the mining income and stays that way for a specified length of time, the contract ends. No different than running your own miner from your own home. If you're mining for profit, you turn it off when it becomes unprofitable.