Vonage monthly cost for a telephone line: $24.95 SIPPHONE costs: however many calls I make plus $0.33 for caller id. Way better deal. Even once Grandcentral starts charging (expect $15 a month) this is still a good deal. SIPHONE Minutes for outbound calls: $0.02 cents a minutes PAP2T ATA for dialtone: $59.95 Inbound calls via …