No customer care number to change plan

Location/place: Sudarshan Nagar/Hyderabad

Name of company/service: Vodafone/voice

I have requested Vodafone to change my plan to have 600 min local with the same price of Rs 199. Since my connection falls under corporate connection plan, customer care (111 from vodafone), can not help. I sent email to [email protected] and there is no phone number to talk and change the plan. Their response is sent some files and choose plan from there. I replied and said, I could not understand and call me to dicuss or give me your phone number to talk. I am getting only email message that choose the plan.
I request you to please help me to change my plan.