@lissovboris Cheers and good luck with this! :-) I have no doubt that you will be able to convince some of them, gradually to use free alternatives, if you continue patiently, taking time to explain.
About #Skype alternatives: I've been using #jitsi over the past two-three years. I managed to convert all of my most important personal contacts, ones I contact on a regular basis. It really worked for both GNU/Linux and Windows using friends. I became good at explaining it and I now got a well written email with screenshots and instructions on how to install and run it. (sadly I still run Skype with Linux Mint on a virtual machine for occasional professional calls where I cannot insist that the other party must install jitsi to talk to me)