You may think that I will write that the clients should contact you the way the feel comfortable. Actually, no. Customers should contact you the way to get qualified support without additional efforts.
So, provide the customers with such channels, where you can provide such support.
For example, we don't have telephone support because I have no idea how this type of support looks like:
— I've got an error here, a red square…
— In which corner? To the left or to the right?
It is much easier to write the letter with screenshots and in a couple of hours receive the thoughtful and verified answer with screenshots, arrows, and video.
Conclusion: the client doesn't need an additional channel if he can't receive help using it.
Social networks are a different story. They can't be ignored. Even though you would like to fence yourself off, the clients will still write something despicable (actually, quite reasonably in most cases). That's why it is necessary to monitor these requests and provide support right there.
First of all, in 99% of cases you will be mentioned due to a certain failure, so you will need to deal with the negativity from those who will come to comment the post. Secondly, it is always a great opportunity to give a masterclass on solving conflicts with customers and gain some positive points to your karma.