Any Idea How To Stop Dtac Music Ring Tones ?

[ThaiLife]

My wife has a mobile phone with a Dtac SIM card, and she has some how set it to use a Dtac supplied music ring tone, which Dtac make a charge for every time its used, she now realizes that its a waste of money ( I told her so ) and wants to remove the music ring tone, she is saying once you sign up for this Dtac music ring tone, you can't stop using it, which I find hard to believe, she has tried speaking to Dtac but not getting any where. Ive tried talking to Dtac, but seem to be also getting no where, I am all most sure you can in fact stop this service with a combination of keyboard numbers etc, does any one know

these keyboard numbers that stop this music ring tone option.

Thanks

TL