The nearest Telus tower is approximately 2KM north of the lake. It should still easily be within range of Skaha Lake. Bell does not have any towers in the entire region. Rogers has a tower that is situated quite high up on a hill and much closer to the lake.
You can see the tower locations here: http://www.ertyu.org/steven_nikkel/cancellsites.html
You mention asking a question but I didn't see a question.
Last time I was through the area I don't recall any reception issues near Skaha Lake. As to why you and some of your friends had reception issues, it would be impossible to say why. Normally the first recommendation is to speak with tech support right away to notify them of the issue. If enough reports come in they'll usually get a field tech to check the tower for issues.