Am I selfish or mean? what should I do?

So I have two guy friends that i have recently been talking to. Guy A and Guy B always ask me if i wanna facetime. They always want me to text them and even double or triple text if i don’t answer. They text me everyday. Guy A sends texts when he sees that i’m not replying and Guy B does the same but gets upset if i don’t answer. I usually reply late since i’m usually not on my phone and I don’t like calls. i hate whenever they ask me if i want to get on a video call. I love my friends but i don’t need to constantly talk to them all the time, or everyday. it’s like they never have things to do ( or anyone else) while i’m always doing something. My sister says i’m a bad friend for feeling like that and makes me feel bad about it ( she usually says i’m a bad friend and that thats why i don’t have many friends) but i just don’t like calling them. Most of the time, it’s just them talking to me. Whenever they ask if i wanna go on a call, i make up excuses. How can i tell them the way i feel without being mean?
Am I selfish or mean? what should I do?
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