How to handle a Corporate Client in Customer Service in a Professional manner?

• One must understand what the customer wants
• One must realize that integrity brings loyalty and trust and ideally this involves being honest and keeping your word with regards to deals that you may pledge to honor.
• Develop and cement relationships with customers so they can continuously choose and recommend your firm.
• Educate and empower your customers that way they get the information they need plus extra.
• Follow up with your customers to make sure both their plans and the business plans are in sync and ideally to develop new business opportunities.
• Let the customers know exactly what your firm is doing for them, be it fixing problems or upcoming events and so on.
• Learn to say no the right way not leaving them with a flat out no but rather being being subtle about it to the extent that regardless of having been told no they still would want to continue with doing business.
• Whatever anyone does we should always be polite.

1. Ap​ologize. A simple, “I'm sorry to hear about this issue,” goes a long way with a client. Even if the issue is not your company's fault, you have a client who is acknowledging a less-than-stellar experience and that, at the very least, deserves an apology. Keep your pride in check and put the client's feelings first.
2. Sympathize. Have you ever had to contact customer service to file a complaint or resolve a situation? Of course you have. So you know how it feels to be on the other end of that correspondence. Tap into that. Put yourself in your client's shoes. You may deal with complaints and issues all day but for your client, this is the single most pressing thing on their mind right now. That mind can be put at ease with a reassuring, “I understand that this can issue can be stressful. But I am here to help.”
3. Let Them Talk.It is likely that your client has already practiced what they want to say to you in regard to their problem. In fact, talking openly about the problem can prove to be quite therapeutic and bring a bit of relief to even the most troubled customer. Open the door for them to speak freely with a simple statement like, “I want to make sure that we get this taken care of. Could you please tell me more about your issue?”
4. Listen.If your job involves interacting with clients all day, it can be tempting to tune out at times. But each customer needs to feel that they are special and that your company is looking out for them. Be a good listener. If the conversation is in person or on the phone, take notes. If you are communicating via email or chat, pay attention during the discourse and re-read the conversation with a goal of quickly and effectively addressing the client's needs. When replying, quote the key points that the client brought out so that they know they are being heard.
5. Promise a Solution. Whether you can solve the problem instantly or not, be sure that your client knows that your mission is to make sure that they end up happy, despite the issue. If you need more time to further work on a solution, offer a note of assurance, such as, “I have all the details I need at this time. I'm going to work with our team to provide you with a solution. You'll be hearing from me soon. If anything comes up in the meantime, here is my contact information.”

I would agree with Mr. Vinod's answer ... Thank You