That's a very clear and popular requirement! Many global virtual assistant companies now offer flexible pricing models with no long-term lock-in contracts to appeal to businesses of all sizes.

Here are a few categories of global options often known for this flexibility:

1. Marketplaces (Highest Flexibility)
These platforms give you maximum flexibility as you hire independent freelancers for specific tasks or on an hourly basis. There are no contracts with a firm, only with the freelancer you choose.

Upwork: A massive global platform where you can find virtual assistants from all over the world. You set the rate and the terms (hourly or fixed-price).

Fiverr / Fiverr Pro: Excellent for project-based work and one-off tasks. You pay per "gig."

Arc (or similar talent networks): Connects you with pre-vetted remote talent globally, often with flexible hourly or contract terms.

2. Companies with "Bucket" or Task-Based Pricing
These firms offer pre-paid hour packages or task-based plans that often do not renew automatically or require a long-term commitment.

TaskBullet: Known for its "bucket system," where you buy hours in advance without a monthly commitment.

Fancy Hands: Primarily suited for quick, on-demand, one-off tasks. Their plans are based on a set number of "requests" per month.

Magic: Offers on-demand virtual assistant services with flexible support.

3. Managed Services with Monthly/Flexible Plans
These companies vet and manage the VAs for you, providing a dedicated assistant and backup support, but they typically offer monthly subscription plans with no long-term contract requirement (month-to-month billing).

Wishup: Provides pre-vetted VAs and often highlights flexible pricing and no recruitment fees.

Time etc: Connects you with experienced US and UK-based professionals and offers various monthly hour plans.

Ocean Outsource / Global Hola / Remote CoWorker: Many offshore (e.g., Philippines, LATAM) BPO/VA firms offer competitive rates with "No Lock-In Contracts" to attract clients.

BELAY: A US-based company that offers month-to-month contracts.

Key Things to Check Before Signing Up:
Contract/Cancellation: Explicitly confirm their cancellation policy. Look for month-to-month or no fixed term.

Minimum Hours: Some "flexible" plans still require a minimum monthly purchase (e.g., 10, 20, or 40 hours).

Setup Fees: Some agencies charge a non-refundable setup/onboarding fee, even if the contract is month-to-month.

Talent Location: VAs from different parts of the world (e.g., US/UK, Philippines, India, Latin America) have different cost structures, time zone availability, and specific skill sets.