"As long your account is active you can continue mining bitcoins with this company without any issues." Unfortunately this is not true. You should be honest and refer to the recent trouble with bitcoin mining lifetime contracts of hashflare that were cutted by this company to 1 year limited - without a warning, within a very short period of time (not even 24h). And they don't even honor old contracts. They just changed the rules to their advantage.
And the newest information: they are out of sha256-contracts, which means you are not even able to re-invest...
If you wanna gain new customers by referal, thats ok, but you should be honest with them about the conditions of those companies you are recommending.