The conditions are constantly changing
Save money: This is why you should change your mobile plan even if you are satisfied
There is reason to continuously explore the offerings.
It is always good to perhaps once a year take a look at the offerings and compare prices with the plan you have, even if you are satisfied with what you have. Mobile operators change their prices continuously, while new operators, often smaller challengers, emerge. However, it's not just about looking at what other operators offer. If your operator changes their plans, it's not certain that you as an existing customer will benefit from any price reductions. Therefore, signing a new subscription even with the operator where you are already a customer can allow you to lower your monthly costs or get more for the same amount you are already paying.
Another reason to switch or at least review which subscription you have is, of course, if your needs have changed. Perhaps you notice more and more often that your data allowance runs out, or conversely, that you have an unnecessarily generous amount of data that you rarely or never use. Both situations are good signals that it's time to switch to something better or cheaper.