Constellation Energy stopped by my house one day same thing a few months ago. Seemed legit, we switched, no problems so far. Cheaper bill, still comes from BGE.
This seems to be what I've gathered from my readings. They're competitors for gas (and/or electric). Confident in what they're saying is true. They're wanting to switch you over to their supply while BGE remains the provider and distributor of it. Since my apartment we only pay a small amount of gas and electric (heat and hot water are included) there's not much sense in switching over.
I'm smarter than my roommate so instead of engaging them in a lenghthy conversation I just tell them I'm not in charge of that particular bill and no he's not home to talk. I've had a few different companies try to come to the door and ask about it... sometimes they're male... white/black younger/older sometimes they're women.
Pretty sure no one wants any identities considering the block I live on is dirt poor and filled with section 8 people. Couldn't open a pay day loan in our names let alone get a real loan...