Nokia 7500 prism balance tone

Question

Treated myself to a nokia 7500 prism when i bought my husband the n95 and its good but although all my extra tones are switched off i keep getting a service message with my balance after every text i send. it uses the same tone as my received messages too, which if im busy driving or something can be annoying because i think iv received a text. is there any way i can stop it or do i have to just get used to it. thanks for any help.