In general, there are no disadvantages as such of having a good unlimited plan connected to your network because it is a very cost-effective solution of using phones and internet these days.
However, there are some disadvantages attached to having free cell phone services. For example, in some schemes, customers do not have the choice to select the smartphone they want.
They often don’t get the latest model and the quality is somewhat lower than other models available.
In private offers, customers may get phones that are not demanded by people in general or have some technical incapacity due to which they want to dispose of them off. So keep these factors in mind before you opt for a free cell phone service.