The rental charge will either be: 849x5/31 + 999x26/31 or 849x6/31 + 999x25/31depending on whether Jan 6 was under new or old plan.If it was under old plan, you free day time quota for Jan 1 to 6 would be 1.25GBx6/31 which is roughly 250 MB. If you exceeded this, you will be charged @ Re 1 per MB.Your night usage on the 6th is appearing because you are no more under the NU plan. From that point on, you only pay rent.