Polwii Bluetooth mic not connecting to iPhone

I recently bought a polwii bluetooth mic kit from Amazon and watched a video online of it before purchasing it, but when I plug the receiver into my iPhone, the audio doesn’t switch over to the microphone. It’s meant to be a plug and play, plug the receiver in and in 3sec it’s meant to be working. Does anyone know or have any idea what is wrong and how I could fix this issue.