I have a 18, 16, 15 and twin 9 year Olds what I do if they leave there stuff around I bin it, also I tell them if they want pocket money I will give them £30 a month each if every day they do at least 1 chore in the house, as for phones mine know if they don't hand it over not only will they be grounded but I will smash one of there other valued possessions up, it took a while for them to realise I'm the adult and they will listen but it works