change of plan without intimation

Location/place: India

Name of company/service: vodafone

Dear Sir/Madam,
i have taken vodafone connection with CUG plan for LnT Corporate connection. as per the introduction letter it was conveyed that the plan is 1 paise per min i.e VG_MU_MV_L&T_75S plan. however due course and without intimation the plan was changed to 1 paise per second. this is not acceptable as service was promised to me by vodafone at 1 paise per minute. this sudden change as caused losses and unwanted in connivance.