That problem is now in the past. We got one of these cordless phone systems that connects to my phone via Bluetooth. Now, when my phone rings, it also rings on both handsets, one upstairs and one down. It's really loud and hard to miss, which is a good thing because sometimes I just don't hear the cell phone, especially when I 'm in the other room. And, when I leave my phone downstairs and my son calls (somehow he seems to do this regularly), I can still answer the phone and talk to him. It's been really convenient, and I keep wondering why we didn't do this sooner. I know these phones have been around for a while, but I just didn't think to check into it.
I know our cell phone company offers a 'home phone' service, which is a separate line and costs $20/month, but this does the exact same thing with no new phone number and no monthly charge. The cost of the phone system itself is only a couple month's worth of service, and additional handsets (the system is expandable up to 5 handsets) are only $20, so if you need more than 2 handsets, they pay for themselves in just a month or two. That is, if you're thinking of adding a home phone service like this. If you're still paying for a traditional landline, this is a great way to save a lot of money - unless the cost of phone service has decreased significantly since we stopped using it, which I doubt - by cancelling that service and still keeping the convenience of having a home phone.