Is it permissible to circumvent the "fair usage policy" imposed by telecommunications companies, which slows down internet speed to 40kbps despite advertising an "unlimited internet" service, by using a VPN to improve the speed?

It is not permissible to use technologies that increase internet speed beyond what was agreed upon in the contract, because this violates the terms of the contract and deprives the company of a considerable benefit. Note that describing the service as "unlimited" does not mean unlimited speed, but rather a slower speed as stipulated in the contract. The company's addition of state taxes and its control over prices should not be dealt with through deception, but rather by addressing the competent authorities. Exploitation in adhesion contracts necessitates state intervention to amend or annul the contract.