I understand the limitations leading to why they do it this way in Vietnam, but I don't like it. Had one driver pester me for a few days asking if I needed him to drive me anywhere, especially long distance. Also, a few of the drivers said they didn't want to call a foreign number and drain their SIM cards of value.

I've also had drivers refuse to go to the exact address, but for the most part it's worked well for me, though not well enough to actually pull out my phone vs. hopping into the nearest Vinasun taxi.