There are actually hundreds of reasons but let's focus on ten of the most common reasons why someone calls in to a service center. You want to have your 800 number handy for the company. If it is PG&E, Comcast, AT&T or banks like Wells Fargo, Bank of America or Chase you may have your own record of times you have called.
1) Their service is not working
This could be cable, phone, internet, power, plumbing or something they use daily. Some will do basic troubleshooting, others will not but regardless you will be expected to use your Jedi power to correct it.
2) They do not agree with their billing statement
This will happen if there are such items as taxes, delivery charges, "handling" or a charge they do not recognize. If billing is not your main duty, get them to a representative in that department, otherwise you could spend thirty minutes going over everything.
3) They have an appointment and the technician has not arrived
This is when you will need the cooperation of another department and a quick response to let the customer know when they can expect them.
4) This could be the second, third or fourth time they have called about the same issue
I know, why did I get this call. If you have notes read through them, find out what has already been done and put your A-team skills and knowledge into overdrive.
5) There were sent something they did not order
This could be a gift from someone or more likely some overzealous sales person "pushed" it on the customer. The order department should be able to correct this.
6) They have a problem with quality of service
When this happens you may want to alert management to see if others are calling about this issue or similar ones. Document what it is they are not happy with.
7) There is a misunderstanding what was to be done
Nothing is more annoying to a customer who orders say internet service and the tech arrives and says I'm here to install your new phone line. Get on the horn with the sales department and get the order corrected and have them set a new appointment ASAP.
8) They are just calling to gripe
There are some customers who have nothing better to do. Listen patiently and hear them out. Check any notes to see if they have been issued credits, as they may frequently call just for that reason.
9) Services were removed in error
Oh my, someone made an error somewhere. This may not take a couple hours but perhaps days. Credit for the inconvenience will be in order here.
10) They are complaining about a salesperson or a fellow representative's attitude
Take this as a way to be a hero. Resolve whatever issue they have and you will have the caller thinking I should call this person every time.