ok guys ive been doing this trick for a while but if you play osrs mobile you'll see that you can buy membership/bonds with google play.
Hence there is an Phone app called google opinion rewards that gives you money for answering easy question ; sometimes about youtube, sometimes about places you've visited which are tracked through phone GPS. Basically I get about 12 bucks a month which feeds my OSRS monthly addiction. In addition when you basically subscribe to a month (AKA buy a month) Jagex will only try to tap into your google play balance which at that point will be not be 11 dollars aka not enough for a month. With that being said because you don't have a balance Jagex will keep your membership for 6-7 days after your month until it is cancelled. After you get your google play money again, rinse and repeat.