It's hard for everyone because the whole world is learning English but not so many native English speakers learn other languages. They get flooded with requests. There aren't many native English speakers here who learn Persian, so you might be more successful in finding fellow English learners to practise with.

If your target language is English, it would be very hard to find a native speaker to practice with. It is simply because only a small number of English speakers are passionate about acquiring a new second language in comparison with a large number of English learners. 

Furthermore, learning a language does not have to find a native speaker to practice with given a wide variety of English learning materials are available online. 

I do agree with everyone else's comments. There are way more people trying to learn English than the other way around. That being said, there just aren't enough Native English speakers to go around. Additionally, learning a second language isn't a big thing in the US. When I was in high school, I did all right in Spanish class but I didn't remember much once I graduated. Studying a foreign language isn't a requirement to graduate from college too so there has been a steady decrease of people who study a foreign language in college. If you spoke a popular language, such as Spanish, French or German, you may find someone to practice with. Otherwise, moving to an English speaking country would be your best option to improve and/or master your English.