Let's say I am using skype, but I cannot video call someone because my camera will not work. Is it correct to say it like: I can only voice call you? Tell me please the most common and natural way native speakers would say it.
This is a new technology, so there may not be established idioms. Something like "I can only voice-call you" is understandable, in context ("my camera's broken so...")
There is a pattern in which, as new tech is invented, we have to invent new word to distinguish the old tech. For example, 40 years ago a "phone" had a circular dial. When push-button, and later mobile and smart-phones were invented, we had to create the terms "rotary phone", and "landline" for the old tech.
Similarly, before Skype (etc), everyone knew what "call someone" meant. But now we can also "video call" we have to invent a new term for "non-video call". Saying "voice-call" seems reasonable.