Disappointment with Vodafone's Slow Internet

Dear Vodafone,

My problem is not being solved, and I am sorry that I decided to use your service. Even after testing with a dozen different mobile devices, the internet on any of them is painfully slow. The speeds I'm getting can drop as low as 5 Mbps at times. Your representatives insist there is no issue after conducting measurements, despite the fact that you have reported problems with the internet and that the interruptions occur frequently. This is extremely annoying, and I require a solution to this problem as quickly as possible.