The Fr.39 your landlord is charging you is for providing the socket and some basic TV and internet. The Fr.59 you’re paying is for more TV, faster internet and/or a landline.
That means your actual UPC package is (59+39) Fr.98/month.
Am I right that you’ve been with UPC for more than a year? It was about a year ago that they decided to make a change that most landlords seemed unaware of. The change involved you paying everything (Fr.98/month) and your landlord nothing. The landlord then removes this cost from the Nebenkosten and hence stops cross-charging you.
You could check the new UPC bundles and if you see something you like for less than you’re paying now (Fr.98 in total) then ring up and ask to change. However, if not, it’s easiest to just stay as you are.
However … if you’re a new UPC customer and you have a bill of only Fr.59 including the connection fee (the cheapest I can see today is Fr.69 for 50Mbit so it does look like you’re on a Fr.98 package) then your landlord needs to stop charging you the Fr.39 as he/she is not being billed for that. UPC will give you a letter to hand to your landlord that explains it. You’ll need to ring UPC and ask for one.