Don't keep trying to flush a blocked toilet. Each flush adds more water, and if it's completely blocked, it'll overflow onto the bathroom floor. Just leave it and call us.
If it's close to overflowing, turn the isolation valve on the pipe feeding the cistern (usually on the wall behind or beside the toilet). This stops more water getting into the cistern so nobody can accidentally flush it while you're waiting.
If it's already overflowed, mop it up with old towels (not your good ones). Toilet overflow is contaminated water, so wash your hands thoroughly and bin the towels if they're past saving. Disinfect the floor after.
Don't pour bleach, drain cleaner, or chemical unblockers down a blocked toilet. They don't work on solid blockages, they make the water caustic (dangerous for us), and they damage old pipes. Just leave it for us to clear mechanically.
If you've got another toilet in the house, check if that's draining fine. If both are blocked, the problem's in the shared stack pipe or the outside drain, not the individual toilets. Tell us when you call so we bring the right kit.