Remove spl char from the phone number

Hi Experts,

I've the below script for which i need to eliminate special characters like(_.-,&,$ etc) in the number.

I tried adding "REGEXP_REPLACE" but it is saying "NOT Valid".

Please let me know if this can be sorted out.

<quer:substring>

  <quer:replaceNullOrNot>

   <quer:field path="Candidate,HomePhone"/>

   <quer:field path="Candidate,HomePhone"/>

   <quer:replaceNullOrNot>

    <quer:field path="Candidate,WorkPhone"/>

    <quer:field path="Candidate,WorkPhone"/>

    <quer:replaceNullOrNot>

     <quer:field path="Candidate,MobilePhone"/>

     <quer:field path="Candidate,MobilePhone"/>

     <quer:replaceNullOrNot>

      <quer:field path="Candidate,PagerPhone"/>

      <quer:field path="Candidate,PagerPhone"/>

      <quer:string/>

     </quer:replaceNullOrNot>

    </quer:replaceNullOrNot>

   </quer:replaceNullOrNot>

  </quer:replaceNullOrNot>