MTNL trump is prepaid mobile service which is provided in all four metros of India. It is quite good in cellular service but you will find it very difficult to recharge it as there is only MTNL Mumbai/Delhi is only providing online recharge facility.
You will find a lot of websites claiming that recharge your MTNL phone online, but reality is different after doing registration you will find that there is no option to recharge MTNL TRUMP or they will give some links of another website.
Some website are selling like purchase online MTNL prepaid PIN, but these claims are only for fooling you.
So please note that if you are using MTNL prepaid in Mumbai then only you can do online recharge other wise there is no option.
I hope MTNL in other cities will provide online recharge facility in future :).
Please do not waste your time to recharge your MTNL TRUMP online if it not belong to MTNL Mumbai and Delhi.