Help with 'pausing' SSI

I've been getting SSI, not disability, straight SSI for 2 years now. At the time I applied I was in rough shape. On SSI your able to work up to 20 hours per week and not have it affect your pay from the government. Now I have the opportunity, plus being mentally and physically able to do so, to get a government job with Fema. The pay is around $30/hour but obviously could not do that kind of job part time and also on SSI. Does anyone know if I can put a hold on my SSI and work again for a few years? I'm only 58. When I was approved for SSI, they told me I couldn't continue to try to get ssdi, which was what I was applying for. I can never get through to a live person at the local office. Hoped someone had some insight