How can I prevent Numbers spreadsheet from changing cell format when adding new costs?

Hi,

I have been struggling with Numbers as it seems to change cell format to automatic all the time. I have really basic spreadsheet to calculate household costs and even though I have changed even the whole column format to "currency" Numbers from time to time changes the format to automatic. I would understand this if I would paste some formatted data to cell, but I am just inputting costs by inputting the cost without any extra characters and pressing enter at the end. Mostly this happens when entering costs between old ones. I am rearranging lines to insert costs, so my costs are in correct order. If I have few lines where ALL lines are formatted the same way, why rearranging the lines changes the cell formats back to automatic?

Is there some way to force the column cells to stay in intended format?

[Re-Titled by Moderator]