Dear Mr Smith, 
I am writing with 
a 
great disappointment about the recent damage your dog has done in my garden. 
Your pet often Correct article usage
apply
cross
 the fence and Change the verb form
crosses
play
 in my garden area, everything was fine Correct subject-verb agreement
plays
untill
 Correct your spelling
until
last
 week, when he started thrashing all the flowers in the area, I have Linking Words
also
 Linking Words
seem
 him digging a hole which caused Correct your spelling
seen
the 
major damage to all the plants which led to uprooting of few. 
It would be great if you Correct article usage
apply
can
 keep him in the designated place using his collar chain, as it would prevent him Wrong verb form
could
to jump
 and Change preposition
from jumping
come
 over. Wrong verb form
coming
Linking Words
As well as
 your pet toy is damaged and he does not enjoy it as much Rephrase
Also
he
 Correct word choice
as he
use
 to, so you could consider getting him a new one to increase Change the form of the verb
used
him
 engagement.
It is hard to say, if the issue Change the pronoun
his
persist
 I might have to inform the authorities and file a formal Change the verb form
persists
complain
 about the future incident.
Look forward Replace the word
complaint
for
 your kind Change preposition
to
corporation
 on Correct your spelling
cooperation
this
. 
Yours sincerely, 
Narender SinghLinking Words