Hi KellyM41
Each contract is for a minimum term length which is generally either 18 months or 24 months. Any discounts you receive will either end on the date indicated as when your minimum term length is reached, although sometimes the discounts expire before that date.
Once the minimum term end date is reached you will therefore lose any existing discounts and will need to negotiate a new deal. Its'best to contact VM 30 days before this date so yuo can either negotiate the new deal, or commence your 30 days notice period.
Each bill you receive, and your online contract state the minimum term period and discount end dates.