If a government is completely blocking internet and still the user is trying to access it with the help of such connections might be the reason of legal action against the user.
If a government is completely blocking the internet in order to suppress and control its population, then I would haven no issues attempting to bypass those restrictions and fight for my freedom, including the financial freedom that bitcoin brings.
In such a scenario, people would likely turn to alternative means of communication and transactions, such as using cash (in many countries, card payments on POS systems and ATMs may also be affected). Plus, a widespread internet blackout can have far-reaching consequences beyond personal finances and communication. It can potentially disrupt essential services such as emergency response systems, transportation, and logistics, making it difficult for people to access medical care, food, and other essentials.
Any internet blackout would likely simply prevent access to the outside world, like China or North Korea already do to various degrees. Systems like national banking or emergency response could easily continue to run.