在国外，真正决定手机网速的是什么

Because what stands between you and the mast changed. Walls, metal-coated glass, your position inside a building and even which way you face all alter the quality of the received signal. The two spots may also be attached to different cells or different bands. Large differences over short distances are entirely normal.

Not necessarily. Price usually reflects the amount of data, the validity and the number of countries covered rather than speed. Speed in any given minute is set mainly by network conditions where you stand. The one case where buying more genuinely helps is when your allowance ran out and you are being throttled.

The indicator says the phone registered on that technology, not how much capacity it received. On a busy cell or at a distance from the mast the result can still be low. What you are doing may also be limited by latency or by the service's own servers, and changing radio technology does not address either.

No. Leave it automatic as a rule, so the phone can move to a better cell as you travel. Manual selection is a troubleshooting tool for when you suspect the wrong operator, and you should return to automatic afterwards, or the phone will hold onto your choice even as the signal degrades.

Each test pulls real data in order to measure, so it draws from your allowance. Repeated tests on a limited plan add up, so test enough to establish a pattern rather than every time something feels slow.

It can. Such settings restrict background activity and often reduce image or video quality, which people read as a slow connection. While troubleshooting, switch it off briefly to see whether the symptom changes, then decide whether to leave it on.

Several reasons: a different operator, the priority gap between local customers and roaming users, and the bands each handset supports.

Only if the slowness came from throttling after a cap. If the cause is congestion or signal, a different plan changes nothing.