In case you suspect someone is intercepting your calls or messages, there are steps you can take to make sure that your conversations or chats are not compromised:

Use encrypted calls and chats - End-to-end encryption (E2EE) keeps messages and calls encrypted and private from everyone, including the provider of the messaging service. The sender is one “end” of the conversation and the recipient is the other “end”, which leads to the name “end-to-end”. It's like when you send a scrambled letter through a postal service, nobody can read your letter except you and the person to whom you sent it.

One of the benefits of E2EE chat apps is that you can easily connect to your contacts without additional steps like public key exchange for PGP emails. The following apps offer end-to-end encrypted chats by default:

Signal is a free and open-source application developed by an independent non-profit organisation, which means it does not contain ads or trackers within the app. Some of the useful features of the app are disappearing messages, it is available for both mobile and desktop, and supports proxy access (if Signal is blocked in a country).

Element is a free and open-source chat solution, built on Matrix, an open network for secure, decentralised communication. Some of the perks of Element are that it can be self-hosted, it's good for organisational implementation because it is easily scalable, and there are free and paid versions.

WhatsApp is free to use but a proprietary app, which is available on mobile, desktop, and web alike. WhatsApp is owned by Meta, Facebook’s parent company, which doesn't provide a sense of privacy because its business model is based on selling user data. It has some useful features like disappearing messages.