You can. Whether you should is a different question, and the answer turns on what you would be giving up rather than on what it costs.
Alberta uses designated agency. The REALTOR® whose name is on the sign is the seller's designated agent — that individual represents the seller personally, and owes the seller loyalty, confidentiality and their best advice on price. It is not the brokerage that represents them; it is that person.
So asking them to also act for you is asking one person to advise both sides of the same negotiation, which is not something they can do.
Alberta's answer is transaction brokerage. Both you and the seller must consent in writing, and from that point the agent stops advocating for either of you. They facilitate: they prepare paperwork, pass information along and keep the deal moving.
What you lose is advice on price and strategy — how far below asking to go, what the comparable sales really say, what the seller's situation suggests. That advice is the single most valuable thing a buyer's REALTOR® provides, and it is precisely what transaction brokerage removes.
The alternative some buyers end up in is being an unrepresented customer: the listing agent keeps representing the seller and owes you honesty and fair dealing, but no advice and no advocacy at all.
Usually not in the way people expect. The seller's compensation arrangement is set in their listing agreement before you appear, and whether their brokerage discounts it when acting on both sides is between the seller and that brokerage — you have no say in it and no guarantee of seeing it. Meanwhile buyer representation is typically compensated out of that same published amount, so having your own REALTOR® generally does not add a cost. How a buyer's REALTOR® is paid →
Give up representation for a saving that is not yours to collect and you have made the worst trade available in the transaction.