Wish to avoid using 03458780900 to contact Affinity Water, Hertfordshire.  The alternative 0800 numbers listed on Saynoto.... do not work (for me). Any help will be much appreciated.

Why do you wish to avoid calling an 03 number? Calls to 03 numbers are inclusive in allowances on landlines and on mobiles on the same basis as calls to 01 and 02 numbers or are otherwise charged at "geographic rate" - the same as calling 01 and 02 numbers. If you have an inclusive allowance, individual calls incur no charge.

If you're calling from outside the UK then 03 numbers don't always work properly  and/or may be charged incorrectly but that's the only possible exception to what Ian01 has said.

KC wrote on Sep 17^th, 2018 at 2:39pm:

Wish to avoid using 03458780900 to contact Affinity Water, Hertfordshire.  The alternative 0800 numbers listed on Saynoto.... do not work (for me). Any help will be much appreciated.

You could e-mail them here