Day light *******

I dn't know how longer will i complain about vodacom my installment was R275 when i took my contract now its R285 which i never even asked questions about.So this month my installment its R516 when i call they telling me its for advance know wanna called me to tell me this, we never had an agreement about such when i took my contract this was not mentioned, i wanna pay my advance cash or with airtime i can't afford to pay R516. I had R136 when i cancelled my advance with them and i owed R186 so i wanna pay that R186 and i want my installment to be tje same amount when i had an agreement of applying for my contract.