Whether dealing with paralegals or other staff, you are completely responsible for all business entrusted to you, and must maintain personal and actual control and management of your office. In other words, you must maintain direct supervision over every non-lawyer staff member (BC Code, Chapter 6, rule 6.1-1). For example: you act for a claimant in a motor vehicle accident case. You assign the file to your paralegal for the purposes of routine correspondence between the parties to the dispute, including phone conversations. You fail to review and authorize consent to disclosure of documents and your paralegal consents and discloses the documents on your behalf. The disclosure is not in the best interest of your client.
In addition to the disclosure problem, one of the challenges you face is that while a client will appreciate receiving a smaller bill, a client also has the expectations, when going to a law firm, that a lawyer will deal with their matter. If the client only ever has communications with a paralegal, it can lead to dissatisfaction and complaints to the Law Society. Always remember that the accountability for improper delegation of work rests on your shoulders!
Note: This is not to say that assigning the work to the paralegal is incorrect. It is perfectly acceptable to do so within the scope of the BC Code provisions, but you must still supervise their work and should remain cognizant that some clients will expect (or demand) lawyer contact.