I had Free for some time back in 2016. After I had SFR, I went with them because I needed a new cell phone after mine had been stolen from my pocket while I was shopping in Zara.
I had a proper contract and everything. I ended up ditching them when my cell phone was stolen from the hands of a kid I was with on ligne 8 right when the doors were closing. This is what they do, wait for the buzzer, then snatch it right out of your hands and leap out as the doors close. I saw another guy get this done to him one night when I was again on the ligne 8 near Bastille traveling back to École Militaire.
Anyway I ditched them because their customer service sucked, and I couldn’t get any help dealing with a service I could no longer use. I ended up going back to SFR but using their prepaid service. I wouldn’t recommend it. It’s crazy expensive. 35€ for 60GB of data. You can try the other sans contract service (SFR Red) but you need a RIB to set it up. And you can’t get help from them either (why is Bouygues the only provider with English speaking customer service agents?!).
I ended up going back to Free because they offer 100GB for 19,99€ a month (the most GB for the lowest price). And I didn’t have to actually talk to anyone to get it.
You go to their only store location in the 8th (near Madeleine), let them know you’re just there for a SIM and then you go to the self serve kiosk. You get a SIM in like 3-5 minutes. No need to show paperwork, or sign a contract. Tourists can even do it (you can get service from a month or longer). There are also cheaper price points. I went with the 19,99€ plan because I need the most data I can get. But you need a credit card. It doesn’t accept cash.
I actually met two Filipino ladies who couldn’t purchase a SIM or pay their bill so I ended taking their euros and paying with my credit card. I know how hard life is when you don’t have a credit card so if you’re ever being asked, maybe have some empathy.