Appalling service

I've had endless problems with Onespark and this causes me a lot of anxiety I've been with them for some time now,my policy was cancelled then reinstated,premiums were increased incorrectly and that was fixed and now we back to new issues,I'm being double debited which is leaving me out of pocket and resersing the debit order comes with bank charges,this has happened before where I was charged an incorrect premium and another one was collected I was told to reverse the incorrect premium and now I'm being double debited,I'm left wondering if this company is legit and if I'll the get the cover I need should the unthinkable happen,they always call me to accept debit order mandates when I already have a mandate in place with them and now they are double debiting my account