Is there a free alternative to using Facebook Messenger bulk messaging softwares?

I was looking for a way to automate messaging people through my Facebook profile (personal account and not Facebook page). We have a farm and they resell our fruits. Facebook Messenger API only allows messaging friends and people who interacted with your page. I want to give one last chat blast through my personal account and ask them to message our Facebook page if they want to keep updated about our harvests.

This was the only one that worked so far: AutoNetworks Facebook Message Sender By Anh-Anh. It only needs a list of facebook profile IDs. Is there a free alternative? Can be freeware or some instructions on how to code it. I don't know how to fill the Messenger chatbox with the text I want to blast.