I contacted BBB on several occasions and have mixed feelings about them. There seems to be a pattern in how they contact or rate businesses.
Where they failed me (and others):
When my complaints were against big business, BBB has always 'sided' with the big business. Even after I supplied ALL the evidence in support of my complaint, they closed my complaint with comment, "customer did not respond"! And that happened not only with me, but also with a numerous other people. A cursory look at the complaints against the big businesses will reveal that.
Where they helped me:
When my complaints were against some (really) small business. Ironically, one complaint was closed with comment, "the business did not respond" where actually it was I who did not respond to the resolution offered by the business! But other than that, I got a more than a few disputes resolved through BBB with small businesses.