Unless there is good reason, for example health and safety requirements, then your employer should not restrict you from wearing religious symbols at work. It will be relevant if the symbol is not strictly required by your religion, for example in the case of a cross which is worn by personal preference if you are Christian. For most religious symbols such as hijabs, turbans or bangles, you should speak to your employer about making an exception to the dress code to accommodate you. If your employer is not willing to make such an exception, or to make adjustments to the dress code as needed, then you should seek advice as soon as possible.