minimum gas coming in to worcester bsch 241?

Ive had to get bosch out to my boiler 3 times in 2 yrs and every time they come out they say my gas pressures are too low. My last invoice says- increased min gas from 0.2 to 2.0mb as boiler struggling to light. This is costing me about £200 every time to get bosch out. I was wondering would this be included in a service as that would work out cheaper or is this something i can fix myself.