Payment price change

Hello sorry for disturbing you, please I will don’t understand why my price on my bulb application phone change again. Isnt fair somebody to choose with my money how much I will paid. My account it is on credit 58,04£. Im not on minus to change my price for next month. 176£. When I will be on minus off course I will paid, but for the moment Im on plus. I refused to paid the price for next month 176£. Thanks

I just change my price on 159£ from 176£