The promotional data will be provided to you every month (depending on the promotion), starting on the date the mobile service was activated. Note that promotional data for the 1st month will be fully provided on the date of mobile service activation, as entitlement for the 1st month. Promotional data will automatically cease after the last day of the month of the promotional period.
For example, you have signed up for a Free 80GB for first 3 months promotion, and your mobile service was activated on 25th Jan 2021. You will get 80GB promotional data for use in the remaining days of Jan 2021. On 1st Feb 2021, your promotional data will restart and you will enjoy 80GB for the month of Feb. For Mar, you will enjoy the last entitlement of the 80GB promotional data till 31st Mar 2021 2359. You will no longer have the 80GB promotional data in Apr.