Text messages coming in from my own phone number

On occasion I'm receiving text messages from people - but it's not coming in from their phone number, it's coming in from my own. Right now, I have a client who is texting me about work and their messages are coming in from my number not theirs. If I send them a message using their own phone number, the reply comes in from me. This is very frustrating. Any idea how I can stop this from happening. (several times a year it seems this occurs and I can't find a solution online)

(I'm in Canada - using Telus Mobility, I have an iphone 12)