Candid Society review for Postscript SMS Marketing

I changed to their new plan - "charge by usage" - like four days ago, to save some money because I didn't use SMS Marketing as much. I went from paying $50 a month, to being charged $987 in three days out of nowhere. I literally sent out two campaigns and have 511 subscribers. Before this, I used this app occasionally and it went well, but this was outrageous.