Maybe; maybe not. I know, you hate this kind of answer but it is a bit more complicated, and depends on a few things that you did not mention in your question. (Be sure to complain about this practice by the law firm to the lawyers if it bothers you as explained at the end of this answer.)
Do you have a written fee agreement (aka retainer agreement) with the law firm? If the client (you) are an individual then one is required under California Business & Professions Code section 6148. If there is an agreement, is it one that complies with the B&P Code? If not then it can be declared "void" by the client.
If there is no retainer agreement or if the ones that exist can be declared void then the answer is that law firms are entitled to a "reasonable fee" and this is something that is usually determined by the number of hours (or fractions of an hour) of time by a lawyer or a cerftified paralegal multiplied by the prevaling market rate. So if you call and speak to a paralegal and he/she devotes 12 minutes to speaking with you about your matter then that is 2/10ths of an hour and this times a reasonable paralegal rate (say $100 per hour) is the fee for that time. Same thing for lawyers at the firm but at a higher rate. NOT okay for secretaries or clerks. The time and expense for these types of (very important and necessary) support workers is included ion the hourly rates of the profesionals (who are sometimes caled "timekeepers") who record their time and charge for it by the 1/10 of an hour units. If your call was very brief--say one or two minutes-- then the time for that should not exceed 1/10th of an hour and if the law firm uses a high minimum increment of 2/10th of an hours or 1/4 hour then you should also complain about this as well AND mark down the time by re-writing the time on the copy of the bill.
If you do this exercise of sending in a marked-up copy of a bill once you will get a good idea of how reasonable your lawyer is. Do not be afraid to do this but do not be "jerk" in the way you write to the lawyer.
Now if you have a fee agreement that is valid then the language of that agreement is very crucial to answering your question. IF the agreement is one that was explained to you and IF it has language that the time for some kinds of clerical staff will be billed and if this does not happen in a way that is "unconscionable" as that word is defined by RPC 4-200, then it is probably okay for the law firm to do this. There are some kinds of law practices that are set up to have very experienced staff do a good deal of the work especially in interacting with clients and IF they do their jobs sell it is probably less expensive than talking wih the main lawyer who is probably billing his/her time at many times the rate for staff or paralegals.
Now here is the important thing: You have the right to answers to your concerns. ASK in writing in a polite but firm way about these charges for clerical time. Do NOT just pay the bill without an explanation. You can always request mandatory fee arbitration under California law but you may not want to do this if you are otherwise satisfied with the lawyer. You can also pay the undisputed portion of the bill and see what happens. It is best to make your complaints in writing and the best way I have seen is to make a copy of the bill and write your commments on the individual entries that you are concerend about (on the copy) and send this to the law firm (but be sure to make a copy of your marked up copy) for your records. Put the words "clerical time" or something similar next to the entries that you find objectionable. If the time is higher than you remember (for the call) then mention that also and write down the time to the correct amount.
Be brave, firm but polite and fair in your letter. Do this in writng. Keep copies of everything.
You and your attorney should have a written agreement or engagement letter that provides an explanation of the attorney's billing practices. If it was disclosed to you, and attorney can charge for staff time.
