[Serusers] Authentication prefix

I need to cut leading "00" and ad a prefix "123" to an outgoing call to allow authentication to provider. I tried several scripts but non of them works. Can somebody help me? Thanks from a SER novize! Regards Christian

Last one:

# send out 00 prefix to wholesale psnt termination VOIP if (uri=~"^sip:00[0-9].*@.*") { if (!is_user_in("From", "ld")) { sl_send_reply("403", "Payment required"); break; strip(2); prefix("123"); }; setflag(1); rewritehostport("64.xxx.xxx.76:5060"); if (!t_relay()) { sl_reply_error(); }; break; };