Go and buy a toilet plunger from a DIY store, put in the toilet and pump up and down. It will cost you a fiver at most. If you call a plumber you can multiply that by 10.
If all else fails go back to DIY store and buy a bottle of One-Shot. Ignore the instructions about dosing, pour in the whole bottle. Leave for 20 mins then hopefully blockage will have gone. Treat very carefully this is concentrated acid, wear gloves and do not inhale fumes. Pour extremely carefully so no splashing. Keep children out while it's soaking.
I cleared all toilet blockages in my four B & B premises for years and years with these two methods and never had to pay a plumber for this particular job.