This may be a solution. I read the reviews on Amazon, and the first one mentioned that it performed much better with RG6 cable. When I had the house built, I had a RG6 cable installed for dish tv, but never used it. May be perfect for this as it is separated from the house. I suppose Consumer Cellular can confirm it will work. I read that you have to register the things now.

You could get something like this, but it's a bit expensive: Amazon.com: zBoost ZB545 SOHO Dual Band Cell Phone Signal Booster for Home and Office, up to 2,500 sq. ft.: Cell Phones & Accessories

I use Consumer Cellular and my house seems to block our signal. Four bars outside, 1-2 bars inside. Is there anything I can get to improve this? Our house was built with reflective insulation, etc.