Ivy didn't mention if he wants an app for free or a paid one. English Central can be used for free and you have access to more than 10.000 videos and myriad of exercises for learning vocabulary. If you go premium, you can't have language partners, but you can have native teacher partners. Every time you reach around 500 points you get 20 minutes lesson with native English speakers in real time. In order to achieve 500 points all you have to do is to watch and do the exercises related to the videos. If you watch 5 or 6 videos per week you surpass this number. It's very easy to get the lessons with native teachers. They announce it for $15,00, but you can get a discount. I got it for 8,00. It's really worthwhile trying it.

P.S. If you prefer to have it for free, you have a limit of two videos per day, but lots of exercises from each video.

Hello talk in android and apple store.