"Look, Matěj, that is not possible!"
Translation:Podívejte se, Matěji, to není možné!
It's not just first names vs formal address, it's more complicated. There is no strict dividing line. Sometimes we use first names + formal pronoun/verb forms, usually in semi-formal situations eg. at work or at school - a person in a position of authority is more likely to use it.
Your boss may ask you for the report about XX: Matěji, přineste mi, prosím, tu zprávu ohledně XXX. 'Matěj, bring me the report on XXX, please'
Your teacher at a upper secondary school may address you: Dominiko, už zase jste nenapsala test z chemie! To už je potřetí! 'Dominika, you haven't passed your chemistry test yet again! That's the third time!'
From a little bit of googling: apparently yes there is the "Hamburger Sie" which is using formal + first name and there is the "Münchner Du" which is using informal + last name. I have never heard of them before and judging by their name they are probably regional around Hamburg and Munich respectively.
However, I've noticed that when English films/series are translated into German, it can happen that every "you" is translated as German "du", Czech "ty", even when it wouldn't be appropriate at all but I considered this to be translation errors and not proper German.
It's not common, but possible. I personally don't have anyone in my life whom I would address formally (vy) and use their first name at the same time. Nor do I know anyone who'd do that to me – I'd consider it weird and would try to change it to mutual "ty" asap. The formula is (and has been all 40 years of my life) quite simple for me: "first name = ty", "Mr./Mrs. last name = vy". I've mostly only encountered this hybrid "Vy, Matěji..." usage in movies, with rare exceptions - the only one I can think of is my tutor at the university. She was a young woman (probably 35) and I was around 21, she was my superior and my mentor. She used my first name to address me, but she used "vy" to keep it formal, polite, and "academic". I still used her last name + "vy", so it wasn't symmetrical. About a year later, we finally agreed on using "ty". She's the only one I can think of in my life - but I think it's quite an apropriate example: When two colleagues (especially if one is a superior) want to be friendly and formal (no beer-buddies) at the same time, they can choose this intermediate address.