how do i remove warning on my reputation.
You cannot remove the trust rating on your profile. Only the person who gave it to you can remove it. Contact them (in this case Vod), however it is higly unlikely that they will remove it.
All i did was asked for a really small loan without collateral a few months ago..
Asking a loan without collateral is not allowed on the forum. Imagine you are taking a loan from a bank - its just the same here. You need to provide a valid collateral to the lender - which has value higher than the loan amount so that in case you are unable to return the loan in future, they can resell it and get back some money. Is this too difficult to understand or are you trying to beg for some petty cash?
Any idea how to get rid of it?
Read what I wrote above.
since you got it from vod, you can try in a month's time assuming what he posted in this thread still holds true:
https://bitcointalk.org/index.php?topic=887515.0and it looks like it was more than just a few months ago, it's almost been a year since he's tagged you.
Possibly the account was sold by the original owner because of this negative trust and now someone bought it and found it out.