Unfortunately, you don't get to have your own 1-900 number if you choose the Mystic.
The Mystic is a good shaman class that primarily uses wards to prevent damage from ever coming into the target. They also use an array of powerful buffs that improves every aspect of their allies, boosting statistics to high levels. They're also one of the strongest debuffing classes in the game, with slows and other abilities unparalleled by any class. They're a valuable addition to any group, as they are capable of turning some of the most ferocious monsters in the dungeons of Norrath into weak and helpless creatures struggling to swipe at your tank. Mystics also have disease and cold based damage over time spells, many of which have strong debuff components that make the monsters more vulnerable and less dangerous.
Mystics are one of the strongest soloing priests, as their wards and damage over time spells along with their slows and debuffs makes them able to chew through monsters fairly quickly at little risk to themselves. Their buffs also help push them over the stats that most classes have, making them both durable and offensively dangerous. In groups, the Mystic's primary role is to buff their allies, keep wards up and make their foes as weak as possible. While they can serve as main healers, they are most effective and efficient as secondary healers and focused debuffers, as constantly casting heals interrupts their ability to perform those other roles. Mystics have a fast casting group heal, but it should only be used in emergencies, as it will draw a lot of threat to you.
Spells like the level 65 Bolster greatly improve the attributes, size and health of a single target for a short duration. Minor Auspice and the spells that come after it boost both health and power - a spell that comes in handy when you cast it on your whole group. They can cast group damage wards and single target damage wards, which is one of their primary spells for use in raiding - it greatly improves the efficiency of healing, providing synergy with the wards that a Paladin healer provides. They're also strong area of effect debuffers, as the Dreadful Lethargy line slows an entire group of monsters - very powerful for area of effect groups. The Enfeeble line reduces the strength and stamina of a target, making them easier to kill and less dangerous to the tank. Mystics can also transform into a bear, improving their physical statistics.