How can a mortagag company sell my loan to other companies?

My mortgage is now being in the hands of Wells Fargo. I used a Morgage Company to buy my present home, they sold it without my knowledge, then that company after collecting one months mortgage payment, finally sold it to Wells. How can they make those transactions without my knowledge plus I never signed one mortgage paper to the last two buyers. I know this just can't be right--I think that somebody needs to look how these are bought and sold without the knowledge of the buyer and without any signatures - more or less-I didn't even have a say-so who should have my mortgage in the first place-it is a FHA and Wells is serviciing it right now--How can do business without the customers signature or knowledge???? Mystery??