Moving in to the new apartment on 1st June and electricity company says: moving date should be after it 14th June

Hi everyone, So as from the title, I am moving to a new apartment on 1st of June but when I am trying to get electricity for the new apartment from Check24. It says the new move in date must be after 14th of June. So if I activate the electricity now , will they start the contract from 14June ? I live in Hagen and the main/regional electricity provider here is “Mark-E” which is expensive. So my question is that from 1st June till 14 June which company electricity will I use if I do the contract with E.on company.