Hi --- Perhaps a letter that is stern and more to the point would suffice, write to them recorded stating that unless they give a satisfactory justifiable reply to your simple question in a reasonable time, that you will consider them to be in breach of their original agreement, and therefore reduce your monthly payments in accordance with the original terms of the agreement.
Explain also that you appreciate they may be busy; the same as yourself, but if they give a credibe explanation that it will in the long run save them from more work, by solving the problem once and for all if they provide, "due care and skill" to your request as they are obliged to under, "the sale of services act", which accompanies the sale of goods act.