I do not own any sonoff devices myself but i believe sonoff is the same as ewelink right? If so it would most likely be possible using sequematic.com. You can either use the webhook trigger directly or you can use the variable change/modified trigger and change the variable through webhook. I personally prefer the latter because it let's you combine multiple functions into one sequence.
Another possible way would be to use autovoice plugins "trigger Alexa routine" action, for that you will also need the Alexa app though and set up routines in there, making it a bit convoluted. I believe it requires a one time payment aswell, atleast for unlimited use, you might be able to use it without paying but if i remember correctly that requires you to watch an add every 8 hours or so.
