First said its new SimpliCITY scheme will see services from the big peripheral housing schemes in to the city centre merged, renumbered and run more frequently.
The bus giant admits its new scheme will involve a slight cutback in the overall volume of services, but insists most passengers will see an improvement.
But passengers are now expressing fears that these changes will involve fare increases, which they already consider too high.
Katarzyna Michalowska, 27, a support worker from Springburn said: "Let's hope there aren't any more price increases. I think the buses are too expensive as it is.
"I think the changes in the routes might cause another increase, but I really hope not."
At the moment, a single "short hop" fare with First in Glasgow – up to five stops – costs £1.15, while a "longer hop" anywhere within the city cost £1.85.
A return in one Glasgow city zone costs £3, £3.45 for both city zones, while an all day ticket costs £4.50.
There are also price variations for travel in the Dumbarton, Kirkintilloch and Cumbernauld zones.
Ryan Breslin, 21, a plumber from Summerston, said: "If the buses are going to be going longer routes then they will probably put the prices up again."
Full-time mum Emily McKechnie, 21, from Milngavie, said: "If there was another price increase, I wouldn't be happy."
Meanwhile, Glasgow councillors have also voiced concerns about the prospect of any price rise.
Greater Pollok councillor David McDonald, said: "It was around this time last year that First increased fares by an eye watering 27%. My constituents are worried about the possibility of another increase."
In response, First Glasgow Managing Director, Ronnie Park, said: "Our efforts are focused on delivering a significantly better and simpler bus network.
"We are very conscious to offer value for money fares and we do hope to announce some promotions in the coming weeks to encourage as many customers as possible on to our services."