Hi roses - as a senior citizen there might be some avenues you could explore - I don't know whereabouts you live, but a lot of councils now take part in this scheme https://www.gov.uk/garden-maintenance-council-tenants, you can put your postcode in and see.
Also Age UK may be able to help - some of their local offices have gardening volunteers etc.
Or you could try contacting your nearest agricultural or horticultural college - they may be training their students and need just this sort of task for them to tackle - they may be happy to sort it out for you, maybe for a small donation to a charity of their choice or something.
Don't give up, keep trying and we'll keep trying along with you. If you let us know roughly whereabouts you are, someone might just have some local knowledge.
Just a thought: It goes without saying (but I'll say it anyway) be very wary of chaps who come to the door unbidden offering to do such jobs - don't let them do anything without getting a proper reference from someone they've worked for before - that should be someone you can contact and speak to about how they did the job, how they cleared up after themselves and how much they charged (and whether they added any 'extras') .
Age UK and many local councils have 'Trusted Trader' schemes which may be helpful.