CCG Mining or Hashflare
I am not an expert in cloud mining but I manage to find you a link that explain in details what you might want to know. https://bitcoinmining-cloud.com
As you have already mentioned, CCG Mining or Hashflare are trusted but I like to add a word of caution => When engaging in any type of cryptocurrency mining there are risks, but profitability is possible if you make the right choices.
A promo code is just a marketing tool to get you involve in the program or plan. Investors should only invest in cloud mining if they are comfortable with these risks - as the saying goes, never invest more than you are willing to lose.