Terrible billing system

In March I upgraded to 5G, activated on the first guess it was an April fools thing as it has not worked even though my area apparently shows that it's covered for 5G (worked elsewhere though) I cancelled on the 4th of April within the 7 day period but I was still billed between the 1st-11th. I was assured by one of the agents that it will be credited but still nothing to date.