Could be poor signal in the phone modem, a hardware problem or house wiring. Best bet is to contact Shaw and they can look at your phone modem levels and do a reset.
@HeleneCh -- garbled audio in landline
To whom were you talking? Another Shaw Phone customer? Somebody with a TELUS land-line? Somebody on their mobile-phone, in an area with a poor cellular connection? Somebody with their own VOIP (Voice Over Internet Protocol) adapter slaved to their cable-modem?
Consistently? Only certain friends? Is there a pattern?