increase in direct debit before i even start

I recently signed up and was told my direct debit would be for £59 however before i have even finished switching to you i have now received an email saying my direct debit will be £70? how can this be already changing when i havent even moved to yourselves yet

Its an estimate based on having no readings from you. It will still take 70 as the first payment but you can adjust it right after that to what you think you will use.