I don't know what PM's official position is, but I personally think (and hope) there would not be an issue when we mention other companies' services. I've done so on occasion, and I've received no indications that suggest otherwise. PM employees might understandably never recommend using a competitor's services, but it's an important distinction that we members are customers first, not employees.
Is there a company that can serve every customer's needs perfectly? Such a thing does not exist. If I were a potential or current customer looking for options to best suit my needs, I'd want any members to provide advice openly in good faith. After all, if this community routinely gave advice against the best interests of customers, that would reflect badly on the community, and on Public Mobile. Such a negative image would do more damage to the PM brand than is worth any gains made by encouraging unsuitable purchases. When we as a community deal with each other and potential customers honestly and openly, the reputation that results is worth far more to PM than anything gained by restricting advice. That kind of goodwill can't be bought.
By no means is PM a perfect company. Those of us who have been part of the community for any significant amount of time certainly know there is room for improvement. But I'm active in this community because I'm a happy customer and I believe in PM's product and business model overall. As long PM operates honestly and I'm allowed to participate and give advice freely, then I see no reason for that to change. 
