You have several needs:
o home landline
o home office landline with fax
o cellular service
o international calling
o lower your phone bill
o telemarketer block
If you have a fast stable broadband ISP (like fiber or cable) and a home LAN with a good router that you manage, then you can learn about DIY BYOD VoIP, get an account with a good ITSP like
VoIP.ms or CallCentric or others, buy an OBi202 or 302, and setup comprehensive and flexible phone service that you administrate. Once you have it working, you can port your existing numbers and cancel your existing service at your own pace. You will get more features, more control, and pay much less. This will also lead you to cheaper International calling, and could help you to discover ways to improve your cellular usage and costs. Your BYOD VoIP solution can also include multiple sites and mobile devices.
This is a learning process that you will need to pursue to reap the full rewards. Do-able and well worth it, imo, but not plug and play if you want to do it fully.
The OBi is an analog telephone adapter (ata) that can 'connect' your existing house telephone wiring and phones to your LAN. It permits you to continue using your existing telephone equipment. The OBi ata is a good starting point and a fine ata with many features and a polished design... it's worth working with. Later, you can consider IP phones that connect directly to your LAN for more business like features and better audio quality than some traditional consumer grade telephones... but more expensive and decentralized configuration for small users.
Alarm service and faxing and other services that expect to communicate over traditional telephone service 'might' have issues communicating over VoIP. You'll have to trust but verify.
Traditional phone service is regulated PSTN or POTS over copper. Lately, it's becoming POTS over fiber, but still regulated. Regulation is state cost control/oversight... a good thing but still costly.
New voice service is unregulated digital products... VoIP over cable or fiber. No regulation and no cost control... and not as reliable as copper POTS. The big telcos want to bundle it with TV and Internet to obfuscate their pricing. The cheaper retail spinoffs offer a discounted plug and play version with fixed capability.
It's all going to become VoIP. You can stick with the big players and pay more for less; switch to the discount plug and play providers and pay more for less; or you can do it yourself, bring your own device, and pay less for more.
An OBi will cost you ~$70. An ITSP deposit will cost you ~$25. Then you will have enough to build your phone service and try it out for 2-3 months. Google Voice is free calling but there are many considerations you will eventually realize... for starters, no 911 service. One nice thing about DIY VoIP is that you can mixed in additional ITSPs for failover, backup, or best cost routing.
Search Google for VoIP forums. Find a helpful active one and lurk to begin learning.
Hope that ummm...helps.