I’m lucky as I have a 15 and an 8 year old who are respectful and help out. We’ve been strict parents from when they were babies but it’s more like tough love rather than authoritarian. I don’t think you can raise kids by letting them have their own way all the time from babies and then expect them to suddenly change when they get to their teens. I’m not saying you have done that but lots of parents do. Some people won’t say no to their kids right from a young age and you are setting yourself up for problems later on in life. My 8 year old knows that he has to clear up after himself, tidy his room etc and that he isn’t allowed his tablet during the school week even if he gets angry about it. They both have a small list of chores that they do to help (feed the dog, empty the dishwasher etc). We have lots of days out and fun times so they can see that you have to balance work with play time.
Kids will have a hard time once they get jobs if they can’t be respectful and take instruction.
I would write up a weeks timetable of what you expect from each of them but also include things you will do for them. If they do it for a month, you could organise a treat for them. Try to explain how much upset they are causing you.
If they don’t listen or refuse, tell them you will cancel their phone contracts so that they can’t use their data, turn off the WiFi and that you will be buying the bare minimum food shop so no treats, chocolate, crisps etc plus no pocket money or play dates. The main thing is, you need to stick to it for a month and go through with any threats - don’t back down. If that doesn’t work, go on strike and do no cooking or washing and book yourself into a B&B for the weekend but don’t tell them how long you are going for.
Good luck!