Asslam-o-Alaikum,
الجواب وبالله التوفيق
If the job you are doing for this firm does not involve interest at all i.e. you do not become part of the interest based transactions or supporting it in any way, then working with your current firm is permissible and the salary you receive as a result is considered halal.
واللہ اعلم بالصواب
