Vodafone Lacks Providing Useful, Definitive Customer Service

I recently transferred my Vodafone number, and it's only been 6 days since the switch. Customer service assured me, "There are no other promotions; prices will increase at the New Year." Surprisingly, the next day, they introduced new campaigns at significantly lower prices. The signal quality and internet speed are stuck in the Middle Ages. Every time I talk to customer service about the issue, the call gets dropped. Then, expressing my dissatisfaction, I called customer service and stated my intention to terminate the commitment within the legal 14-day period. However, they insisted on imposing a 300 TL cancellation fee. Now, I want to clarify: do we have the right to cancel within the first 14 days? Customer representatives are not providing a definitive answer. Please assist me; otherwise, I'll switch to another provider and take legal action to avoid paying the cancellation fee.