Cheap method to answer phone calls via bluetooth

Hi, how I can control my phone, basic controls like answer/end phone calls + pause/next song using arduino and a cheap module

I know that RN52 can do this but it's also 30$ .. Too much

What is the cheapest method to do it ? Excepting the method witch involve an app on the phone.

Also, what is the name of this feature ? A2DP?