Depends upon which weeds are at your place and whether or not the product you used is effective against them.

please post pictures
Oh yes, and tell us where you live.

Where in the United States are you?
Whether any plant poison will control unwanted plant growth depends on which unwanted plant that is, and that can be somewhat dependent on where you are.

Although the formula these companies use may be stronger or different, but based on my experience, it still takes several treatments, up to 1 or more, to get a yard under control, depending on the level of weeds. The reason is that at this time of year, treatment may be used for existing weeds, but new weeds could still be coming up.

If you stay on the program for at least 1 year, then you can at least have gone through the entire spraying phases of what that company can do for you.

It certainly doesn't hurt for you to do some by hand or with your own chemicals.

At the same time, many of these companies do have a satisfaction guarantee, and if you feel one of the outings was not as effective as it could have been, you should call them and talk to them about it.

I'd really urge you to reconsider using a lawn service, TruGreen in particular. You cannot believe the horror stories, I've encountered with this company. A consultation client that had her entire yard sprayed with an herbicide (mistakenly - should have been a fertilizer application). Much of the plantings were killed or severely damaged and the hoops she had to go through for the company even to admit responsibility, let alone compensate her for the damage, was unbelievable. Another - not even a TG customer - who had her lawn oversprayed by a sloppy and somewhat belligerent technician working next door and that resulted in her small dog needing an emergency trip to the vet. And I could go on but the short story is these companies are in business to boost sales and make bucks so they sell you services you don't need, that often require follow up "treatments" to achieve any positive results and that are applied by poorly trained, unknowing (and often uncaring) technicians. Your money would be much better spent by investing in appropriate materials and products to do the work yourself.

A healthy lawn is most able to outcompete weed development so it may be appropriate for you to check out the GW lawn care forums. There's some very knowledgable folks participating there and they can help you get your lawn into shape to keep weeds - most of them - at bay.

While time consuming, manual removal of weeds is always appropriate. If that is too troublesome, then do spot weeding with an appropriate herbicide for the type of weeds present. Blanket applications are seldom efficient and can be harmful and weed and feeds should be avoided - period. And you need to be able to identify the weeds and know when the best time is to apply these chemicals.

But please, stay away from TruGreen and others of its ilk.

I would go a step further and ask if it really is important that your mowed areas contain only 1 kind of grass? According to who? IMVHO, life's way to short to spend on such a meaningless (and usually toxic) endeavor. Mow whatever's there, keep more of your hard-earned $, then move on to more enjoyable and/or productive activities.

Most of the plants we're now told are weeds used to be dinner. If it was more profitable to cultivate/sell them instead of kill them, they still would be.