Wireless speed not up to par


We lave Century link 10mbps internet. When watching Netflix it buffers quit a bit. Tech support at Century Link said to stop the buffering, we need to shut off all wireless to phones, tablets, other tvs and to only use it for Netflix. We can turn wireless back on when no longer watching Netflix. We’ve also been told that trees, houses and buildings around our house affect the wireless connectivity.
We were told when upgrading to the 10 that we could use multiple devices. If that’s the case, then I need to go back to the 5mbps we had before and not pay for more mbps.