Just logged into my DTAC online account...
The servive from transferring credit from DTAC post paid to prepaid (Happy) is, funnily enough, called : DTAC to Happy Refill
Not sure if this link will work as I'm logged in at the mo :
https://sonic2.dtac.co.th/bp3/bin/Dspc/HappyRefillIndex
Here are the full details direct from the website :
oday You can share your happiness to happy users through our dtac to happy refill service…
Convenience than ever! Now you can set up automatic refill schedule and amount
Choose automatic refill amount from 20, 50, 100, 200, 300, 400, or 500 Baht per time including VAT (condition: Maximum refill amount is 500 Baht per billing cycle and refill amount must not exceed credit limit with dtac)
Choose automatic refill schedule from weekly to monthly refill
Refill service fee per time per one happy user = 2 Baht excluding VAT
>> Terms and conditions for Topping Up for happy users
1. Users of Postpaid 1800 system as individuals and juristic person (not including corporate organizations and SMEs) must be in service for at least 90 days, are able to top-up call credits to receiving numbers of dtac prepaid mobile phone system.
2. Call credits can be top-up starting from 20 baht, 50 baht, 100 baht, 200 baht, 300 baht, 400 baht and 500 baht each time (VAT included), not over 500 baht each billing cycle and not over the monthly fixed charge. Top-up fee is 2 baht (VAT excluded) per each receiving number.
3. The service provider will collect the call credits sent to the receiving number from the transferring number, including service charge which will be in the billing statement of each month.
4. The receiving number is not able to use the call credits for any discount purposes, promotions and cannot be redeemed or change into cash.
5. Users are responsible for checking the receiving number’s information before transferring the call credits. If an error occurs, users will not be able to claim the call credits in all cases.
6. The service provider reserves the right to change service fee, terms and conditions of service, and further more prohibit users to illegally / unlawfully make profit from using this service, or cancel service as deemed appropriate. It is recommended that the user should study additional information prior to subscribing any service by contacting 1678 dtac call center or
dtac - feel goood
HTH