Hi and thanks so much for the precious information. I get the thing now. Last question, is 4G and LTE the same thing? Cause I can't see the way to force my 5s in 4G There is no option to do that. As you know, there is only 2G, 3G and LTE.
No 4G and LTE are not the same thing.
For Verizon and Sprint, there is:
1x (1xrtt has a theoretical max speed of 144kbps, 1x EVDO can reach 600kbps)
3G (theoretical max speed of around 2-3mbps)
LTE (Theoretical max of 150mbps through a single channel but something called Carrier Aggregation allows for the use of multiple channels, or bands, at once, allows for speeds of 300mbps and beyond. LTE Advanced or LTE-A involves the use of carrier aggregation. If you hear about XLTE, that's just Verizon's name for high capacity LTE which can reach 150mbps, XLTE isn't an official term)
For T-Mobile and AT&T there is:
GPRS (theoretical max speed of 171kbps)
E (EDGE. Theoretical max speed of 384kbps)
3G (UMTS. Theoretical max speed of about 2-3mbps)
4G (HSPA/HSPA+. Theoretical max speed of 42mbps)
LTE (same as LTE description above)
I believe on iPhones, UMTS, HPSA, and HSPA+ are ALL shown as 4G even though UMTS is a 3G technology. EDGE/2G are often referred to as the same thing but I don't think they are technically. 2G is technically GSM and that only can get to about 10kbps.