How long will a fly infestation last?

I live in a one bedroom ground floor apartment. Two weeks ago I noticed about 5-10 maggots underneath my bathroom mat and some buried in the hallway carpet. Last week I found about 15 brown pupae and by Thursday night 2-3 adult flies followed by a lot of flies in the kitchen on Friday afternoon. I also had some in my living room and bedroom. It's now Saturday morning and there was more killing required in all rooms but not as many as yesterday afternoon. Should I call out an exterminator? One company I spoke to said the infestation will die down after that initial burst on Friday Is this true? I'm concerned they're laying more eggs. Should I get the property treated asap or will it die down as long as I keep killing them quickly. I don't know what the initial host for the eggs was, it's a new build property so unlikely to be any dead animals in the walls or whatever. As it's summer I did have the patio doors open a lot which is maybe how the initial fly got in.