Freebox Move

Okay, I'll try the first solution, the previous tenants moved out three days ago.

Regarding what I wanted to say, no matter what your situation is, whether your line is still active or not, whether you recover it or not, you have every interest in moving your subscription at the same time as you do, and Free has more means than you to track down the numbers of previous tenants, and even former ones before them... If you saw a box during your visit, you likely recognized the operator (Orange? Free? SFR? etc., that can help). In any case, there is a telephone installation in this apartment, so there won't be any issues on that side. You will be able to keep your old number in portability if you currently have a number like 01, 02, etc. Otherwise, you will keep your 09... At worst, a new number will be assigned to you, but it will be free. What can happen next: you were in a totally unbundled zone and will move to a partially unbundled zone (= no more TV, no more V6 box). If it's the opposite, you'll have the choice to keep your Freebox V5 for a while, and then opt for V6 later. If in the new apartment you're farther from a distribution point than where you were before, your bandwidth might suffer. If it's the opposite, you'll have a better speed. But in terms of line length, that applies to all operators...

Well, I tested it with the phone. The voicemail message I received in response: "Your contract does not allow you to make this call."

re
try the online registration process

http://adslcgi.free.fr/subscribe/NDI0_indexnewline.html

with the exact address and the name (you can find that in the mailbox, at the neighbor's, or from the postman, etc. The phone number of the previous tenant should be provided to you. Also check with the agency if that's the case or with the office that manages the rental, or the owners
for free and quite effective. If you get a result, do not go further in the form, close everything and then contact Free by phone in the usual way to explain your specific situation, it's safer
do the same type of procedure with France Telecom, but again don’t go all the way..., you’ll see if they find the same number; keep in mind that the previous tenants might not have had the France Telecom number anymore, but just an SFR, Bouygues or whoever number, hence the importance of knowing which box was there
and if you don't want to bother with these steps, or if you don't have time; then as a last resort:
If you do not know the phone number of the previous occupant's line, please contact the service provided by Free at 0899 905 905 (€1.34 per call, then €0.34 per minute) who will provide it to you, this way your line will be connected much faster, and you will save €19.99 in activation fees.

Otherwise, I do have 0892135151...Maybe they can inform you

So, I called Free, the previous tenants didn't cancel their subscription, well that's in progress.

The person didn't want to give me the phone number....

re
well, no matter what, what you really want to know is if Free finds the number you're looking for.. that's done; they have perfectly located you, and especially the line
the number itself you don't care about...
so you just have to proceed with the change of address request (about a week before moving in), this way you should have your connection fairly quickly at the new home; if necessary, Free will terminate the current line if it hasn't been definitively canceled yet
however, it will be difficult to maintain the connection at the current residence, and to have it too from day one at the new place, I think there will necessarily be a delay, a few days without internet on either side, even juggling as best as possible, because Free is not the only player involved here, it's primarily France Telecom that calls the shots, even if you opt for a line without a subscription with them (total unbundling)

Hello, there are several methods but few work. If the previous tenant left not long ago, you can try to recover their line by plugging in a phone. You dial a number, anything, and a voice will give you a 9-digit phone number to which you should add the "0".

There are solutions proposed on this forum that can help you. But if you have a directory from the year of your visit to the property you are going to, you can find the previous tenant's number or ask the owner for this information.

Hello
Anyway, you have every interest in moving your Free line
On one hand, you won't lose your seniority, and it's free (and it avoids cancellation fees)
Moreover, Free will find the number more easily than you, by cross-referencing your location info, etc. + line transfer info at the distribution point, where you don’t have access
Of course, if you manage to get a result through the owner, a neighbor, or a call as indicated by Tyranausor, that's even better
More info here: https://www.free.fr/assistance/136.html