Bill generation ridiculousness

Location/place: Chennai

Name of company/service: Tata Indicom/Docomo

I wanted my Tata Photon plan changed from 1067 p.m. to 250 p.m. from the month of June. They typically generate a bill for the upcoming month. I tried to contact customer care from the last week of May, but couldn’t get through. And when I finally managed to speak to them on 5th June, they said the bill cycle is past so I will need to pay the old charges for June and the next bill will reflect the changed plan. 8th of July, I get my statement with the old plan still effective. On calling customer care, I am told that the change will reflect only from August, because I had called on 5th June. This is absolutely ridiculous.