iPhone XR microphone issue

Good afternoon. I sent my XR away to have the lower microphone fixed. From what I understand it’s the same part as the charging dock. my reason for sending it for repair was that people couldn’t hear my on cellular calls. But occasionally they could. It arrived back from the repair shop. But I still have the same problem even with a new part fitted. The lower microphone does work on sound recording and Whats app and messager calls. It also works on front and rear video footage. Would anyone know what the issue is please. Thanks