Vodafone — Plan changed without my permission / acknowledgement

Recently my cell phone plan was changed by Vodafone without my consent. I am writing them on email from last week but there is no any response from Vodafone idea and they are keep quite after sending reminder email. Customer care earlier call me and telling we have send email & sms that our plan is change but i have not received any call, email or SMS from them so they told me that we will check with this our back office and will give you response but till now they are not yet replied.