Adding to this... if you have one connection which would require 5Mb, you're already stuck.
You can saturate 1 stream of 4Mb but not beyond since that connection can not be cut in pieces.
If however you have 4 connections of (let's say) 3Mb, you can send them each onto one line, that should theoretically be possible.
(but even then it would not be straightforward to do).
An ISP could do this but even then it requires equipment on your side as well to allow this.
Personal remark: 4Mb for ADSL is rather low. Already in the 90's when I was still working for Alcatel, we had to test those modems for at least 8Mb. That's over 20 years ago !
Shortly after VDSL came out and then it became 20-25mb as norm.
No possibility to move from 4 to 1 line but get a serious boost in performance ?
Or VDSL (same copper pairs, just different technology/modem) ? Just asking ...
I know there are remote areas where this might indeed be a problem. I have a second residence in France where ADSL is at best 2Mb (really pathetic !).
Even with a lousy 3G connection on SXT I can get to 7.5Mb (4G is out of the question or the signal becomes too erratic).
Sometimes you got to work with what you can get and accept it.
The Yemeni government is the only provider of the Internet and a monopoly on it only.
There are only two options:
The first option is ADSL service, which is spread throughout the country. If you want to buy a point, you have to pay $100 without the value of the package. For example, after paying $100 to buy a point with a land line, you have to pay the value of a package. Let's say you want to subscribe to a 4 megabit package, which is the highest stable speed and will not You will receive 4 megabytes, and you will get 3.6 megabytes if the line quality and other factors are good, which costs $150 and has a capacity of 400 gigabytes for a month.
It is true that there is a speed of 8 megabit, but it suffers from many problems, most of the time it goes down to 1 megabit.
The second option is optical fiber "FTTH" This service is available in limited areas that do not exceed 5 areas only, and it is still new, and the price of its installation is $100, excluding the value of the wire and peripheral devices.
As for the packages, they start at $200 for a speed of 25 megabit and a capacity of 200 gigabytes.
And it ends at $670 for a speed of 100 megabit and a capacity of 1 terabytes.