0800 043 8486 is one I have, also from an old email but as you say it directs all requests back to email or website.
I am growing increasingly concerned about Vivo. We have been asking for months for vouchers to be restocked but they only seem to put a very small amount of them in. They also do not respond to support requests. I have two awaiting response from two weeks ago.
Strangely the managing director called me last term to assure me that they had just had a busy season, were a small team and were working flat out. Since we invest about £5000 a year with them on average, and I know other schools in the area do, this rang alarm bells. So much so that last week I looked up their financial records. They did not make happy reading. Our financial director agreed after he had got the report from Company House.
With regard to the xporter tool if it is Groupcall their helpline is useful. If you are exporting from SIMs and are supported by Scomis, then Scomis can usually contact Groupcall to help.