Is it grammatically correct to sign off using “We remain at your service.”? Are the following any better?
We remain at your disposal.
We remain at your disposition.
or remove “remain”:
We are at your service.
We are at your disposal.
or something even better that I haven’t thought of!
Yes, each of those is grammatically correct. The convention regarding
We remain at your service.
is that it’s a relatively short, slightly formal way of saying
We have been in your service, we are now at your service, and will continue to do so as well.
Forever your servant.