Pandit Sethuraman clearly states in "Adhista Vingyanam" that only he who knows palmistry, astrology and face reading (kai rekha sastram, jyotisam, samudrika lakshanam) will be able to grasp the subtleties of numerology. Without the knowledge of these allied sciences, you cannot become a good numerologist.
Secondly, changing the name of a person will alter the karmic field of the person and have a direct bearing on the final karmic destiny of the individual. Fiddling with cosmic energy is fraught with serious consequences and if the numerologist (who suggests the name change) doesn't have Divine Grace (daiva anugraham) then he will be unable to repel the retaliatory karmic wave, leading to unimaginable problems in his own life.
Secondly, changing the name of a person will alter the karmic field of the person and have a direct bearing on the final karmic destiny of the individual. Fiddling with cosmic energy is fraught with serious consequences and if the numerologist (who suggests the name change) doesn't have Divine Grace (daiva anugraham) then he will be unable to repel the retaliatory karmic wave, leading to unimaginable problems in his own life.