Is there such a thing as a Cell Phone Signal Booster?

There are several things you (she) can do:

You can get a broadband RF amplifier. This is appropriate for a situation where you have a faint signal outdoors but it drops to zero indoors. These aren't cheap, but they have several great advantages: they don't care which phone company you use. They support all of them, several phones at once, indiscriminately and simultaneously. No hidden fees or extra charges beyond a few cents a year on electricity. I have personal experience with the fusion 5s, it is absolutely legit. I frequently rely on these at work.

You can get a picocell device. This is a tiny, low-power cellular radio station bridged to an ethernet interface. You need high-speed internet via wire in order to use this. You put it on a bookshelf or wall-mount it in your home, wire it to your home internet and they generally provide for several simultaneous phone calls but only on the specific network that provided the device. The good news is that some phone companies will hand them out for free if you tell them you've got a weak signal in your home. AT&T and T-mobile in particular are known for this. I have one from T-mobile.

Verizon network extender
AT&T Microcell
T-Mobile Personal Cellspot

Sometimes you can use UMTS "Wi-Fi Calling" if you have wi-fi service with a bit of bandwidth available. You need a fairly new phone to do this one. Not all phone companies offer this system.

There are a few other tricks too, but that's most of it. Good luck!

 

Does she have internet service through other means? If so, have her check with her mobile carrier for any possible 'microcell' solutions that work over that internet connection.

Here was one that has been discontinued, but various replacements are discussed:
AT&T Microcell Discontinued: The 5 Best Replacements [2019 Edition]

 

You might read up in this thread : Cell phone signal repeater? | PriusChat

Go slow with the Fi product, as a friend had data charges that were obscene, but others I've met in the mountains swear by it for voice calls.

 

Yes, some cell carriers will provide one for free upon request. T-Mobile is one. I have one at my ranch house out in the country.

 

why did you promise yourself not to post?

 

If there really is NO signal present......a booster won't help.
You can't boost something that doesn't exist.

A booster WITH and external antenna might be required.
But in some circumstances, you are just out of luck.

Might want to call around to some independent cell phone shops in the area, if there are any.

 

Sure.
There are LOTS of them.....
Just log into the Googles and pick the cheapest one you find!

Oh wait....
You want something that WORKS.
That's different.


When you start posting again, fill in some of the blank spots in your friend's situation and you'll get a better idea if you need a femto-cell, booster, WiFi calling solution, etc.....

 

I use a company called Republic Wireless that prioritizes voice over wifi with cell tower as backup. If she has internet service with wifi, her cell phone would work at her home. And it's cheap if you don't use much cell data: $15/mo with no cell data, $5/mo additional per gig.

Not all cell phones are compatible with their service.

 

T-Mobile provides a free booster upon request. My county address is some 40 miles away from Metropolis and who-knows-how-far from a cell tower. It's 2 devices, a receiver that sits at a window, and the re-transmitter that is placed in the home where you talk most often. My signal goes from 1 bar at the window, to 4 bars inside the house.

The only glitch is that once you move from inside to outside the building, the call might drop as signal switches from booster's range to outside signal.

 

T-Mobile is a rotten choice of service provider in much of deep rural Oregon, where even Verizon and AT&T often have spotty service:

 

I agree. Ironically T-Mobile's service out to my country address is better than what I get at my San Antonio city office.