My line is VoIP, not a classic line — is it compatible?

Yes: most business VoIP providers handle forwarding on no-answer and on busy in their settings, often via the web interface rather than a GSM code. We set the delay before forwarding with you — long enough for your front desk to pick up, short enough for the text to leave fast. If your PBX is locked by a provider, we talk to them, or we tell you frankly that it can't be done before billing anything. No known consumer VoIP line blocks forwarding.