Application mobile

I want to integrate a calling system into the application such as Omegle or Azar.

Concept :
A user will be transferred to a call with someone but not randomly! He must choose the topic of conversation and will be on a call with someone who has chosen the same topic.
(I have already implemented the interface).

I just need someone to implement the calling system.
The application is cross-platform. Later I would like to implement this functionality in the web version in Vue.js.
The application is in .net 8 with Maui.
Price : 200$