I got a fully developed Linphone IOS mobileVoip App. Everything is working only problem background calling, when app goes to background - it can not receive anymore call - unless you wake it up . When app is open it works without any issue. Do you think you can resolve it? If you know how to resolve this specific issue then only get on board.
1 freelancer is bidding on average $333 for this job
This can be done, depends of the specifics. Actually, if that's an mobile app, try to check the setup of your phone if it allows to keep the apps in standby.