Ouch… I see… so in your case it is a bit of a problem.
Here are maybe some useful informations but it is unfortunately in German:
https://www.mieterverband.ch/mv/mietrecht-beratung/ratgeber-mietrecht/top-themen/tv-internet.html
My recommandation… call the UPC customer service but be super prepared for that. As the communication is recorded, make sure you explain clearly and in a detailed manner the case with no ambiguity and ask them what they can do.. but do not agree on ordering anything at this point. Take note of the call date and time.
At this point if they said there is no problem and have a solution for you, write UPC a registered letter with what you want to order and under which conditions. Make sure you summarize again the details of the issue and include the reference of the call with the support.
Maybe your case is something common that they are used to deal with easily and if not then you have all proofs of what you asked for and will be able to get it fixed.
Last resort method is to contact the “mieterverband association” or “ASLOCA” in the french part. But then you get yourself into timewasting procedures and discussions and if your landelord is an individual you take the risk of ruining the relation.