Cancellation of the car insurance

I have a car insurance with Discovery insure, last month my premium was increased without me being informed at all, when i called in i was told they cant do anything about it its the annual increase, i then decided to shop around for the insurance when i thought im over priced for the model of car im driving, today i finally find the insurance that is covering my needs at a reasonable price. <br> <br> I called them to advice of my plan to cancel insurance with them, they agreed to cancel without a problem however they will cover until the 28th July instead of 31st July, when i asked why they said i pay my premiums on the 28th of the month and that is the last day of my cover, i then asked how possible it is because that was not the agreement i had when i took the cover, they told me its the new process theyve put in place however i was not informed and why should these changes affect me indirectly.<br> <br> I need then to cover me until the 31st July as agreed instead of them telling me they will pro-rata for the 3 days which i think its sick. i have already agreed with my next insurer the cover will start on the 1st August and i dont need gaps that will be costly for me in case of emergency.<br> <br>