Not paying a debt you legitimately owe doesn’t eliminate the legitimacy of the debt. Most app owners probably won’t take any further action against you because it’s not usually worth the time and money (at least in the US), but they’re entitled to. If they sell your debt to a debt collector, have fun with that.
(Tangent: there is usually a certain number of years of inaction after which they can’t go after you for the debt, unless you again acknowledge the debt. The details and the ways to reset that clock vary by jurisdiction.)
(Tangent: there is usually a certain number of years of inaction after which they can’t go after you for the debt, unless you again acknowledge the debt. The details and the ways to reset that clock vary by jurisdiction.)